p.  W.  FAROliilAR. 

874  OroadwaV;   -   New  V 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/rudimentsofartofOObull 


THE 

RUDIMENTS 

OF  THE 

ART  OF  BUILDING; 

REPRESENTED  IN  FIVE  SECTIONS  I 

I.  The  General  Principles  of  Construction  ; 
II.  Materials  used  in  Building  ; 

III.  Strength  of  Materials  ; 

IV.  Use  of  Materials  ; 

V.  Working  Drawings,  Specifications,  and  Draw- 
ings. 

FOR  the  use  of 


EDITED  BY  JOHN  BULLOCK, 

ilUCHITKCT,  CIVIL  ENGINEER,  MECHANICIAN,  AND  EDITOR  OP  "tHE  AMERICAN  ARTISAN.'  * 


NEW  YORK: 


STRINGER  &  TOWNSEND,  PUBLISHERS, 
222  BROADWAY. 

1853. 


Entered,  according  to  Act  of  Congress,  in  the  year  one  thousand  eight  hundred 
and  fifty-three,  by 

STRINGER   &  TOWNSEND, 
In  the  Clerk's  OfBce  of  the  U.  States  Court  for  the  Southern  District  of  New  York. 


STEREOTYPED  BY  GRIFFIX  A  FARNSWORTfl, 
49  JOHN  STREET,  NEW  YORK 


CONTENTS. 


Section  L— GENERAL  PRINCIPLES  OF  CONSTRUC- 
TION ; 

II.—MATERIALS  USED  IN  BUILDING ; 
«    III.— STRENGTH  OF  MATERIALS  ; 
«    lY.— USE  OF  MATERIALS  ; 

«  Y.— WORKING  DRAWINGS,  SPECIFICATIONS 
AND  DRAWINGS. 

Appendix.— THE  WOODS  OF  NORTH  AMERICA. 


PREFACE. 


It  required  but  a  little  alteration  to  suit  Mr.  Dobson's 
excellent  treatise  to  American  readers.  As  an  elementary 
treatise  it  has  no  equal. 

In  tlie  various  departments,  we  have  made  free  use  of 
Whale's  Series^  copying  from  it  such  information  as  seemed 
appropriate  and  valuable,  sometimes  usiug  the  very  words, 
and  at  others  simply  condensing  its  information. 

It  was  not  without  much  hesitation  that  we  retained  the 
algebraic  signs  made  use  of  in  the  book,  especially  in  section 
I  ;  but  such  readers  as  do  not  understand  them,  may  safely 
omit  them  without  losing  the  substance  of  the  work,  while 
those  to  whom  they  are  familiar  will  find  them  valuable. 

It  is  to  be  regretted  that  authors  make  such  frequent  use 
of  signs  and  terms  in  rudimentary  wocks  as  are  not  familiar 
to  the  general  reader  ;  and  it  is  also  to  be  regretted  that 
the  readers,  and  especially  students,. do  not  acquire  a  know- 
ledge of  those  signs  and  terms. 

This  work  is  intended  as  a  first  book  on  the  art  of 
building,  designed  for  the  use  of  young  persons  who  are 
about  to  commence  their  professional  training  for  any  pur- 
suit connected  with  the  erection  of  buildings  ;  and,  also,  for 
the  use  of  amateurs,  who  wish  to  obtain  a  general  .know- 
ledge of  the  subject,  without  devoting  to  it  the  time  requi- 
site for  the  study  of  the  larger  works  that  have  been  written 
on  the  different  branches  of  construction.'' 


IL 


PRErACE. 


The  list  of  North  American  woods  which  appears  in  the 
appendix,  is  substantially  the  same  as  that  made  by  the  jury 
at  the  London  World^s  Fair.  The  other  tables  are  com- 
piled from  various  sources. 

JOHN  BULLOCK,  Editor. 


APPENDIX. 


WOODS  OF  KORTH  AMERICA. 


1.  Abies  alba,  or  white  spruce ;  weighs  23  lbs.  13  oz.  per  cubic 
foot ;  specific  gravity,  .381. 

2.  Abies  canadensis,  or  hemlock-spruce ;  common  in  Upper 
Canada  ;  weighs  23  lbs.  0  oz.  per  cubic  foot,  and  has  a  specific 
gravity  of  .368. 

3.  Acer  eriocarpum,  or  soft  maple  ;  common  in  Upper  Canada  ; 
weighs  36  lbs.  14  oz.,  and  has  a  specific  gravity  of  .590. 

All  the  above  are  used  in  carpentry. 

4.  Acer  negrundo,  or  box-elder,  ash-leaved  maple ;  common  in 
the  United  States  ;  weighs  24  lbs.  per  cubic  foot,  and  has  a  specific 
gravity  of  .384. 

5.  Acer  rubrum,  or  red  maple  ;  common  in  the  United  States  ; 
weighs  38  lbs.  5  oz,  per  cubic  foot — has  a  specific  gravity  of  .613. 

6.  Ascer  saccharinum,  or  sugar  mable  ;  common  in  the  United 
States ;  weighs  38  lbs.  6  oz.  per  cubic  foot,  and  has  a  specific 
gravity  of  .614. 

7.  Ascer  saccharinum,  or  bird's-eye  maple ;  common  in  Upper 
Canada;  used  in  ornamental  work  by  carpenters  and  joiners;  weighs 
40  lbs.  15  oz.  per  cubic  foot,  and  has  a  specific  gravity  of  .655. 

8.  Curly  maple ;  common  in  Upper  Canada ;  used  in  common 
carpentry  work  ;  has  a  specific  gravity  of  .586,  and  weighs  36  lbs. 
10  oz.  per  cubic  foot. 

9.  Hard  maple ;  also  common  in  Upper  Canada  ;  weighs  39  lbs. 
per  cubic  foot,  and  has  a  specific  gravity  of  .634. 

10.  Betxda  nigra,  or  black  birch  ;  common  in  Upper  Canada  ; 
is  much  used  for  ship-building  in  Canada  and  Nova  Scotia,  but 
is  not  a  durable  wood ;  it  weighs  35  lbs.  7  oz.  per  cubic  foot,  and 
has  a  specific  gravity  of  .567. 


n. 


APPENDIX. 


11.  Birch ;  an  inferior  wood — common  in  Canada  and  the  North- 
ern States ;  weighs  30  lbs.  11  oz.  per  cubic  foot,  and  has  a  specific 
gravity  of  .491. 

12.  Butter  wood ;  used  in  ship-building  ;  has  a  specific  gravity 
of  .460,  and  weighs  28  lbs.  12  oz.  per  cubic  foot. 

13.  Carya  porcina,  or  pignut  hickory ;  common  in  the  United 
States;  is  the  strongesi.  and  best  kind  of  hickory;  it  weighs  49  lbs. 
8  oz.  per  cubic  foot,  and  has  a  specific  gravity  of  .690. 

14.  Carya  sulcata,  or  shell-bark  hickory  ;  common  in  the  United 
States ;  weighs  43  lbs.  2  oz.  per  cubic  foot,  and  has  a  specific 
gravity  of  .690. 

15.  Hickory  ;  common  in  the  United  States  ;  weighs  47  lbs.  8  oz. 
per  cubic  foot,  and  has  a  specific  gravity  of  .760. 

16.  Castanea  vesca,  or  chesnut ;  common  in  the  United  States ; 
has  a  specific  gravity  of  .404,  and  weighs  25  lbs.  4  oz.  per  cubic 
foot. 

17.  Celtis  crassifolia,  or  hack  berry  j  is  a  tough  and  elastic 
wood,  weighing  38  lbs.  6  oz.  per  cubic  foot,  and  has  a  specific 
gravity  of  .614. 

18*  Cerasus  virginiana,  or  wild  cherry ;  common  in  the  United 
States  ;  the  bark  is  used  medicinally  ;  has  a  specific  gravity  of  .515, 
and  weighs  32  lbs.  3  oz.  per  cubic  foot. 

19.  Cerasus  canadensis,  or  red  bud,  Judas  tree ;  a  close-grained 
and  compact  wood,  having  a  specific  gravity  of  .535,  and  weighs 
33  lbs.  7  oz.  per  cubic  foot. 

20.  Cornus  Jlorida,  or  dog-wood ;  a  hard,  close-grained,  and 
strong  wood,  weighing  47  lbs.  4  oz.  per  cubic  foot,  and  having  a 
specific  gravity  of  .756. 

21.  Cupressus  disticha,  or  cypress  ;  common  in  the  United 
States;  grows  to  an  immense  size;  is  much  used  for  shingles;  weighs 
22  lbs.  13  oz.  per  cubic  foot,  and  has  a  specific  gravity  of  .365. 

22.  JDiosyrus  virginiana,  or  persimon ;  a  hard,  close-grained 
wood  ;  weighs  44  lbs.  6  oz.  per  cubic  foot,  and  has  a  specific  gravity 
of  .710. 

23.  Fagus  americana,  or  white  beach ;  common  in  the  United 


APPENDIX. 


HI. 


States  ;  is  used  in  dry  carpentry  ;  weighs  42  lbs.  11  oz.  per  cubic 
foot,  and  has  a  specific  gravity  of  .674. 

24.  Fagus  ferriigina,  or  beech  ;  common  in  Upper  Canada, 
used  in  dry  carpentry  ;  the  wood  has  a  more  rufous  tint  of  color 
than  common  beech ;  it  weighs  36  lbs,  9  oz.  per  cubic  foot,  and  . 
has  a  specific  gravity  of  .585, 

25.  Fraxinus  americanusj  or  American  ash ;  weighs  35  lbs. 
10  oz.  per  cubic  foot,  and  has  a  specific  gravity  of  .570  ,* — is  tough, 
and  elastic, 

26.  White  ash  ;  weighs  30  lbs,  14  oz.  per  cubic  foot,  and  has  a 
specific  gravity  of  .494. 

27.  Gleditschia  triacauthuSy  or  honey  locust :  is  a  very  hard 
wood  and  splits  easily,  having  a  specific  gravity  of  .646,  and 
weighing  40  lbs.  6  oz.  per  cubic  foot. 

28.  Gymnocladus  canadensis,  or  coffee  tree ;  is  a  hard,  compact, 
strong,  and  tough  wood,  having  a  specific  gravity  of  .647,  and 
weighing  40  lbs.  7  oz.  per  cubic  foot. 

29.  Juglans  alba,  or  hickory ;  has  a  specific  gravity  of  .770,  and 
weighs  48  lbs.  2  oz.  per  cubic  foot. 

30.  Juglans  cinerea,  or  butternut ;  has  a  specfiic  gravity  of 
from  .376  to  .487,  and  weighs  from  22  to  30  lbs.  per  cubic  foot, 

31.  White  walnut. 

32.  Juglans  nigra,  or  black  walnut ;  weighs  28  lbs.  15  oz, 
per  cubic  foot,  and  has  a  specific  gravity,  of  .483  It  is  a  strong 
and  tough  wood,  not  liable  to  split,  and  is  much  used  in  carpentry 
work. 

33.  Juniperus  bermudiana,  or  red  or  pencil  cedar ;  is  used  ia 
ship-building  and  for  making  pencils. 

34.  The  Virginia  cedar  is  used  for  the  same  purpose,  but  is  not 
considered  as  good  as  that  from  Bermuda. 

35.  Larixamericana,  or  haclanatack  ;  much  used  and  esteemed 
in  British  North  America  for  ship-building ;  has  a  specific  gravity 
of  about  .600,  and  weighs  about  36  lbs.  per  cubic  foot. 

36.  The  tamarack  is  a  wood  much  used  for  ship-building  iu 


APPENDIX. 


British  North  America ;  it  has  a  specific  gravity  of  ^8^,  and 
weigh  23  lbs.  15  oz.  per  cubic  foot* 

•  37.  Cedar. — The  samples  at  the  World's  Fair  had  a  specific 
grarity  af  from  .294  to  .314,  and  weighed  from  18  lbs.  6  oz.  io 
*  19  lbs.  10  oz.  per  cubic  foot. 

38.  Liriodenron  tidipifera,  or  yellow  poplar;  is  common  in 
the  United  States ;  has  a  specific  gravity  .287,  and  weighs  24  lbs. 
8  oz.  per  cubic  foot. 

39.  Morus  mbra,  or  red  mulberry ;  weighs  35  lbs.  1  oz.  per 
cubic  foot,  and  has  a  specific  gravity  of  .561. 

40.  Nyssa  Multifioray  or  black  gum,  or  sour  gum  ;  weighs  40 
lbs.  6  oz.  per  cubic  foot,  and  has  a  specific  gravity  of  .646. 

41.  Ostrya  virginica,  or  iron  wood  ;  weighs  48  lbs.  11  oz,  per 
cubic  foot,  and  has  a  specific  gravity  of  .779. 

42.  Ficea  balsamea,  or  balsam  ;  is  used  in  carpentry  ;  has  a 
specific  gravity  of  .304,  and  weighs  19  lbs.  per  cubic  foot. 

43.  Pinus  nutts,  or  white  pine ;  has  a  specific  gravity  of  .376, 
and  weighs  23  lbs.  8  oz.  per  cubic  foot. 

44.  Pinus  resinosa,  or  American  red  pine  ;  is  used  in  carpentry  ; 
weighs  26  lbs.  11  oz.  per  cubic  foot,  and  has  a  specific  gravity  of 
.427. 

45.  Ked  Pine ;  is  a  strong  wood  used  in  carpentry  ;  has  a  specific 
gravity  of  .455,  and  weighs  28  lbs.  7  oz.  per  cubic  foot. 

46.  Pinus  rigida,  or  pitch  pine ;  is  a  strong  wood,  weighing 
32  lbs.  per  cubic  foot,  and  having  a  specific  gravity  of  .512. 

47.  Platnnus  occidentalis,  or  buUon-wood,  or  sycamore  ;  is  much 
used  for  making  beadsteads ;:  has  a  specific  gravity  of  .424,  and 
weighs  26  lbs.  8  oz.  per  cubic  foot. 

48.  Populus,  or  poplar ;  is  a  light,  inferior  wood. 

49.  Cherry  wood  ;  weighs  29  lbs.  15  oz.  per  cubic  foot,  and  has 
a  specific  gravity  of  .479. 

50.  Quebec  oak  ;  is  much  used  for  ship  building,  but  is  not  dur- 
able. 


APPENDIX.  V. 

51.  Quercus  alba,  or  white  oak ;  weighs  40  lbs.  per  cubic  foot, 
and  has  a  specific  gravity  of  .64. 

52  Quercus  rubra,  or  red  oak ;  weighs  32  lbs.  2  Oz.  per  cubic 
foot,  and  has  a  specific  gravity  of  .514. 

53.  Quercus  tinctoria,  or  black  oak ;  weighs  34  lbs.  13  oz.,  and 
has  a  specific  gravity  of  .558. 

54.  Quercus  virens,  or  live  oak  ;  is  the  heaviest  and  hardest  of 
the  oaks  ;  has  a  specific  gravity  of  .100,  and  weighs  56  lbs.  4  oz. 
per  cubic  foot. 

55.  Robenia  pseud  acacia,  or  locust,  or  treenail ;  so  called 
because  used  principally  for  treenails. 

56.  Sassafras  officinale,  or  sassafras  tree. 

57.  Tilia  americana,  or  bass-wood  ;  is  even  in  grain,  weighs  25 
lbs.  per  cubic  foot,  and  has  a  specific  gravity  of  .400. 

58.  TJlmus  americana,  or  elm  ;  weighs  36  lbs.  11  oz.  per  cubic 
foot,  and  has  a  specific  gravity  of  .587. 

59.  Red  elm — used  by  wheelwrights. 

60.  White  elm. 

61.  Rock  elm. 

62.  Swamp  elm.    These  elms  are  all  quite  similar. 

63.  Quebec  rock  elm,  or  wych  hazel ;  used  in  ship-building  in 
Canada ;  has  a  specific  gravity  of  .546,  and  weighs  34  lbs.  2  oz. 
per  cubic  foot. 

64.  Uvaria  triloba,  or  paw  paw ;  weighs  51  lbs.  6  oz.  per  cubic 
foot,  and  has  a  specific  gravity  of  .359. 


STONE. 

13  cubic  feet  of  marble  weigh  1  ton. 

13)^  feet  of  granite  weigh  1  ton. 

The  following  table  is  from  Dobson  : — 


VI. 


APPENDIX. 


WEIGHT  OF  TIMBER. 

34  cubic  feet  of  Mahogany  weigh  one  ton. 


39  "  Oak, 

45  "  "  Ash, 

51  "  "  Beech, 

60  "  "  Elm, 

65  "  "  Fir. 


WAGES. 

The  price  of  labor  in  different  portions  of  the  United  States, 
varies  more  than  three  hundred  per  cent. 


RUDIMENTS 

OF  THE 

AET  OF  BUILDIIG. 


SECTION  I. 
GENERAL  PRINCIPLES  OP  CONSTRUCTION. 

FOUNDATIONS. 

1.  In  preparing  the  foundation  for  any  building,  there  are 
two  sources  of  failure  which  must  be  carefully  guarded 
against  :  yiz.,  inequahty  of  settlement,  and  lateral  escape  of 
the  supporting  material  ;  and,  if  these  radical  defects  can  be 
guarded  against,  there  is  scarcely  any  situation  in  which  a 
good  foundation  may  not  be  obtained. 

2.  Natural  Foundations. — The  best  foundation  is  a  natural 
one,  such  as  a  stratum  of  rock,  or  compact  gravel.  If  cir- 
cumstances prevent  the  work  being  commenced  from  the 
same  level  throughout,  the  ground  must  be  carefully  benched 
outj  i.  e.,  cut  into  horizontal  steps,  so  that  the  courses  may 
all  be  perfectly  level.  It  must  also  be  borne  in  mind  that  all 
work  will  settle,  more  or  less,  according  to  the  perfection  of 
the  joints,  and  therefore  in  these  cases  it  is  best  to  bring  up 
the  foundations  to  a  uniform  level,  with  large  blocks  of  stone, 
or  with  concrete,  before  commencing  the  superstructure, 
which  would  otherwise  settle  most  over  the  deepest  parts, 
on  account  of  the  greater  number  of  mortar  joints,  and  thus 
cause  unsightly  fractures,  as  shown  in  fig.  1. 


16 


EUDIMENTS  OF  THE 


Fig.  1. 

'I  • 

1 


aii 

III 

kllillllillllllllllH^ 

3.  Many  soils  fonn  excellent  foundations  wlien  k^t  from 
the  weather,  which  are  worthless  when  this  cannot  be  effected. 
Thus  blue  shale,  which  is  often  so  hard  when  the  ground  is 
first  opened  as  to  require  blasting  with  gunpowder,  will,  after 
a  few  days'  exposure,  slake  and  run  into  sludge.  In  dealing 
with  soils  of  this  kind  nothing  is  required  but  to  keep  them 
from  the  action  of  the  atmosphere.  This  is  best  done  by 
coveriDg  them  with  a  layer  of  concrete,  which  is  an  artificial 
rock,  made  of  sand  and  gravel,  cemented  with  a  small 
quantity  of  lime.  For  want  of  this  precaution  many  build- 
ings have  been  fractured  from  top  to  bottom  by  the  expan- 
sion and  contraction  of  their  clay  foundations  during  the 
alternations  of  drought  and  moisture,  to  which  they  have 
been  exposed  in  successive  seasons. 

4.  Artificial  Foundations, — "Where  the  ground  in  its  natural 
state  is  too  soft  to  bear  the  weight  of  the  proposed  structure, 
recourse  must  be  had  to  artificial  means  of  support,  and,  in 
doing  this,  whatever  mode  of  construction  be  adopted,  the 
principle  must  always  be  that  of  extending  the  bearing  sur- 
face as  much  as  possible  ;  just  in  the  same  way,  that,  by 
placing  a  plank  over  a  dangerous  piece  of  ice,  a  couple  of 
men  can  pass  over  a  spot  which  would  not  bear  the  weight 
of  a  child.  There  are  many  ways  of  doing  this — as  by  a 
thick  layer  of  concrete,  or  by  layers  of  planking,  or  by  a 
net-work  of  timber,  or  these  different  methods  may  be  com- 
bined. The  weight  may  also  be  distributed  over  the  entire 
area  of  the  foundation  by  inverted  arches. 

5.  The  use  of  timber  is  objectionable  where  it  cannot  be 


ART  OF  BUILDING. 


It 


kept  constantly  wet,  as  alternations  of  dryness  and  moisture 
soon  cause  it  to  rot,  and  for  this  reason  concrete  is  very 
extensively  used  in  situations  where  timber  would  be  liable 
to  decay. 

6.  In  the  case  of  a  foundation  partly  natural  and  partly 
artificial,  the  utmost  care  and  circumspection  are  required  to 
avoid  unsightly  fractures  in  the  superstructure  ;  and  it  cannot 
be  too  strongly  impressed  on  the  mind  of  the  reader,  that  it 
is  not  an  unyielding ^  but  a  uniformly  yieldhig  foundation  that 
is  required,  and  that  it  is  not  the  amount,  so  much  as  the 
inequality,  of  settlement  that  does  the  mischief. 

The  second  great  principle  which  we  laid  down  at  the 
commencement  of  this  section  was — To  prevent  the  lateral 
escape  of  the  supporting  material.  This  is  especially 
necessary  when  building  in  running  sand,  or  soft,  buttery  clay, 
which  would  ooze  out  from  below  the  work,  and  allow  the 
superstructure  to  sink.  In  soils  of  this  kind,  in  addition  to 
protecting  the  surface  with  planking,  concrete,  or  timber,  the 
whole  area  of-  the  foundation  must  be  inclosed  with  piles 
driven  close  together  ; — this  is  called  sheet-piling, 

1.  Where  there  is  a  hard  stratum  below  the  soft  ground, 
but  at  too  great  a  depth  to  allow  of  the  sohd  work  being 
brought  up  from  it  without  greater  expense  than  the  cir- 
cumstances of  the  case  will  allow,  it  is  usual  to  drive  down 
wooden  piles,  shod  with  iron,  until  their  bottoms  are  firmly 
fixed  in  the  hard  ground.  The  upper  ends  of  the  piles  are 
then  cut  off  level,  and  covered  with  a  platform  of  timber  on 
which  the  work  is  built  in  the  usual  way. 

8.  "Where  a  firm  foundation  is  required  to  be  formed  in  a 
situation  where  no  firm  bottom  can  be  found  within  an  avail- 
able depth,  piles  are  driven,  to  consolidate  the  mass,  a  few 
feet  apart  over  the  whole  area  of  the  foundation,  which  is 
surrounded  by  a  row  of  sheet-piling  to  prevent  the  escape  of 
the  soil  ;  the  space  between  the  pile  heads  is  then  filled  to 
the  depth  of  several  feet  with  stones  or  concrete,  and  the 

2 


18 


EtJDIMENTS  OF  THE 


whole  is  covered  with  a  timber  platform,  on  which  to  com- 
mence the  solid  work. 

9.  Foundatio7is  in  Water. — Hitherto  we  have  been  de- 
scribing ordinary  foundations  ;  we  now  come  to  those  cases 
in  which  water  interferes  with  the  operations  of  the  builder, 
oftentimes  causing  no  little  trouble,  anxiety,  and  expense. 

Foundations  in  water  may  be  divided  under  three  heads  : 

1st.  Foundations  formed  wholly  with  piles  : 

2d.  Solid  foundations  laid  on  the  surface  of  the  ground, 
either  in  its  natural  state,  or  roughly  leveled  by  dredging  : 

3d.  Solid  foundations  laid  helow  the  surface,  the  ground 
being  laid  dry  by  cofferdams. 

10.  Foundations  formed  wholly  of  Piles, — The  simplest 
foundations  of  this  kind  are  those  formed  by  rows  of  wooden 
piles  braced  together  so  as  to  form  a  skeleton  pier  for  the 
support  of  horizontal  beams  ;  and  this  plan  i»  often  adopted 
in  building  jetties,  piers  of  wooden  bridges,  and  similar  erec- 
tions where  the  expense  precludes  the  adoption  of  a  more 
permanent  mode  of  construction  ;  an  example  of  this  kind  is 
shown  in  fig.  2. 

In  deep  water,  the  bracing  of  the  piles  becomes  a  difficult 
matter,  and  an  ingenious  expedient  for  effecting  this  was 
made  use  of  by  Mr.  Walker,  in  the  erection  of  the  Ouse 
Bridge,  on  the  Leeds  and  Selby  Railway,  a.d.  1840.  This 
consisted  in  rounding  the  piles  to  which  the  braces  are 
attached  for  a  portion  of  their  length,  to  allow  the  cast-iron 
sockets  in  which  they  rest  to  descend  and  take  a  solid  bear- 
ing upon  the  square  shoulders  of  the  brace-piles.  After  the 
brace-piles  were  driven,  the  braces  were  bolted  into  their 
sockets  and  dropped  down  to  their  required  position,  and 
their  upper  ends  were  then  brought  to  their  places  and 
bolted  to  the  superstructure. 


ART  OF  BUILDING. 


19 


I 


Fig.  2. 


m  i  i. 


11.  There  is  always,  however,  a  great  objection  to  the 
use  of  piles  partly  above  and  partly  under  water,  namely, 
that,  from  the  alternations  of  dryness  and  moisture,  they 
soon  decay  at  the  water-line,  and  erections  of  timber  require 
extensive  repairs  from  this  cause.  In  tidal  waters,  too,  they 
are  often  rapidly  destroyed  by  the  worm,  unless  great  ex- 
pense is  undergone  in  sheathing  them  with  copper. 

.  To  obviate  the  inconveniences  attending  the  use  of  timber, 
cast-iron  is  sometimes  used  as  a  material  for  piles  ;  but  this 
again  is  objectionable  in  salt  water,  as  the  action  of  the  sea- 
water  upon  the  iron  converts  it  into  a  soft  substance  which 
can  be  cut  with  a  knife,  resembling  the  Cumberland  lead 
used  for  pencils. 

12.  In  England,  in  situations  where  a  firm  hold  cannot 
be  obtained  for  a  pile  of  the  ordinary  shape,  such  as  shifting 
sand,  MitchelPs  patent  screw-piles  are  used  with  great  ad- 
vantage.   These  piles  terminate  at  the  bottom  in  a  large 


20 


RUDIMENTS  OF  THE 


iron  screw  4  ft.  in  diameter,  which,  being  screwed  into  the 
ground,  gives  a  firm  foot-hold  to  the  pile.  This  is  a  very 
simple  and  efficient  mode  of  obtaining  a  foundation  where  all 
other  means  would  fail,  and  has  been  used  in  erecting  light- 
houses on  sand-banks  with  great  success.  The  Maphn  sand 
light-house  at  the  mouth  of  the  Thames,  and  the  Fleetwood 
light-house,  at  Fleetwood,  in  Lancashire,  both  erected  a.  d. 
1840,  may  be  instanced. 

13.  An  ingenious  system  of  cast-iron  piling  was  adopted 
by  Mr.  Tierney  Clark  in  the  erection  of  the  Town  Pier  at 
Gravesend,  Kent,  a.  d.  1834,  in  forming  a  foundation  for 
the  cast-iron  columns,  supporting  the  superstructure  of  the 
X  head  of  the  pier.  Under  the  site  of  each  column  were 
driven  three  cast-iron  piles,  on  which  an  adjusting  plate  was 
firmly  keyed,  forming  a  broad  base  for  the  support  of  the 
column,  which  was  adjusted  to  its  correct  position,  and  bolted 
down  to  the  adjusting  plate. 

14.  A  kind  of  foundation  on  the  same  principle  as  piling 
has  been  lately  much  used  in  situations  where  ordinary  piling 
cannot  be  resorted  to  with  advantage.  The  method  referred 
to  consists  in  sinking  hollow  cast-iron  cylinders  until  a  hard 
bottom  is  reached.  The  interior  of  the  cylinder  is  then 
pumped  dry,  and  filled  up  with  concrete,  or  some  equally 
solid  material,  thus  making  it  a  solid  pier  on  which  to  erect 
the  superstructure.  The  cylinders  are  made  in  lengths, 
which  are  successively  bolted  together  as  each  previous 
length  is  lowered,  the  excavation  going  on  at  the  bottom,, 
which  is  kept  dry  by  pumping.  It  often  happens,  however, 
in  sinking  through  sand,  that  the  pressure  of  the  water  is 
so  great  as  to  blow  up  the  sand  at  the  bottom  of  the  cylin- 
der ;  and  when  this  is  the  case,  the  operation  is  carried  on 
by  means  of  a  la^ge  auger,  called  a  miser,  which  excavates 
and  brings  up  the  materials  without  the  necessity  of  pumping 
out  the  water.  The  lower  edge  of  the  bottom  length  of 
each  cylinder  is  made  with  a  sharp  edge,  to  enable  it  to 
penetrate  the  soil  with  greater  ea^e,  and  to  enter  the  hard 


ART  OF  BUILDING. 


21 


bottom  stratum  on  which  the  work  is  to  rest.  This  method 
was  adopted  by  Mr.  Kedman  in  the  erection  of  the  Terrace 
Pier  at  Gravesend,  Kent,  finished  a.  d.  1845. 

15.  Before  closing  our  remarks  on  pile  foundations,  we 
must  mention  a  very  curious  system  of  carrying  up  a  founda- 
tion through  loose,  wet  sand,  which  is  practised  in  India  and 
China,  and  is  strictly  analogous  to  the  sinking  of  cast-iron 
cylinders  just  described. 

It  consists  in  sinking  a  series  of  wells  close  together, 
which  are  afterwards  arched  over  separately,  and  covered 
with  a  system  of  vaulting  on  which  the  superstructure  is 
raised.  The  method  of  sinking  these  wells  is  to  dig  down, 
as  far  as  practicable,  without  a  Hning  of  masonry,  or  until 
water  is  reached  ;  a  wooden  curb  is  then  placed  at  the  bot- 
tom of  the  excavation,  and  a  brick  cylinder  raised  upon  it 
to  the  height  of  3  or  4  ft.  above  the  ground.  As  soon  as 
the  work  is  sufficiently  set,  the  curb  and  the  superincumbent 
brick-work  are  lowered  by  excavating  the  ground  under  the 
sides  of  the  curb,  the  peculiarity  of  the  process  being  that 
the  well-sinker  works  under  water,  frequently  remaining  sub- 
merged more  than  a  minute  at  a  time.  These  cylinders  have 
been  occasionally  sunk  to  a  depth  of  40  ft. 

16.  Solid  Foundations  simjply  laid  on  the  Surface  of  the 
Ground. — ^Where  the  site  of  the  intended  structure  is  per- 
fectly firm,  and  there  is  no  danger  of  the  work  being  under- 
mined by  any  scour,  it  will  be  sufficient  to  place  the  materi- 
als on  the  natural  bottom,  the  inequalities  of  surface  being 
first  removed  by  dredging  or  blasting. 

It.  Pierre  perdue. — The  simplest  mode  of  proceeding  is  to 
throw  down  masses  of  stone  at  random  over  the  site  of  the 
work  until  the  mass  reaches  the  surface  of  the  water,  above 
which  the  work  can  be  carried  on  in  the  usual  manner. 
This  is  called  a  foundation  of  "  pierre  perdue/^  ov  rsindom 
work,  and  is  used  for  breakwaters,  foundations  of  sea-walls, 
and- similar  works. 


22 


KUDIMENTS  OF  THE 


18.  Coursed  Masonry. — Another  way,  much  used  in  har- 
bor work,  is  to  build  up  the  work  from  the  bottom  (which 
must  be  first  roughly  levied)  with  large  stones,  carefully 
lowered  into  their  places  ;  and  this  is  a  very  successful 
method  where  the  stones  are  of  sufficient  size  and  weight  to 
enable  the  work  to  withstand  the  run  of  the  sea.  The  diving- 
bell  affords  a  ready  means  of  verifying  the  position  of  each 
stone  as  it  is  lowered. 

19.  Beton. — On  the  continent,  foundations  under  water 
are  frequently  executed  with  blocks  of  beton  or  hydraulic 
concrete,  which  has  the  property  of  setting  under  water. 
The  site  of  the  work  is  first  inclosed  with  a  row  of  sheet 
piling,  which  protects  the  beton  from  disturbance  until  it  has 
set.  This  system  is  of  very  ancient  date,  being  described  by 
Vitruvius,  and  was  practised  by  the  Romans,  who  have  left 
us  many  examples  of  it  on  the  coast  of  Italy.  The  French 
engineers  have  used  beton  in  the  works  at  Algiers,  in  large 
blocks  of  324  cubic  feet,  which  were  floated  out  and  allowed 
to  drop  into  their  places  from  slings.  This  method,  which 
proved  perfectly  successful,  was  adopted  in  consequence  of 
the  smaller  blocks  first  used  being  displaced  and  destroyed 
by  the  force  of  the  sea. 

20.  Caissons. — A  caisson  is  a  chest  of  timber,  which  is 
floated  over  the  site  of  the  work,  and,  being  kept  in  its  place 
by  guide  piles,  is  loaded  with  stone  until  it  rests  firmly  on 
the  ground.  The  masonry  is  then  built  on  the  bottom  of 
the  caisson,  and  when  the  work  reaches  the  level  of  the 
water  the  sides  of  the  caisson  are  removed. 

This  method  of  building  has  been  much  used  on  the  conti- 
nent of  Europe. 

21.  An  improvement  on  the  above  method  consists  in 
dredging  out  the  ground  to  a  considerable  depth,  and  put- 
ting in  a  thick  layer  of  beton  on  which  to  rest  the  bottom  of 
the  caisson. 

22.  There  is  a  third  method  of  applying  caissons  which  is 


ART  OF  BUILDING. 


23 


practised  on  the  continent  of  Europe,  and  which  is  free  from 
the  objections  which  commonly  attend  the  use  of  caissons. 
A  firm  foundation  is  first  formed  by  driving  piles  a  few  feet 
apart  over  the  whole  site  of  the  foundation.  The  tops  of 
the  piles  are  then  sawn  off  under  water  just  enough  above 
the  ground  to  allow  of  their  being  all  cut  to  the  same  level. 
The  caisson  is  then  floated  over  the  piles,  and,  when  in  its 
proper  position,  is  sunk  upon  them,  being  kept  in  its  place 
by  a  few  piles  left  standing  above  the  others,  the  water  be- 
ing kept  out  of  the  caisson  by  a  kind  of  well,  constructed 
round  each  of  these  internal  guide  piles,  which  are  built  up 
into  the  masonry.  This  method  of  building  in  caissons  on 
pile  foundations  is  shown  in  figs.  3  and  4.    The  piers  of  the 

Fig.  3. 


i  I  i  !  j  !  i  I  i  I 
Pont  du  Val  Benoit  at  Liege,  built  a.  d.  1842,  which  car- 
ries the  railway  across  the  Meuse,  have  been  built  on  pile 
foundations,  in  the  manner  here  described. 

Fio;.  4. 


V  V  V  V   V  V 
23.   Solid  Foundations  laid  in  Cofferdam. — lliere  are 
many  circumstances  under  which  it  becomes  necessary  to 


24 


RUDIMENTS  OF  THE 


lay  the  bottom  dry  before  commencing  operations.  This  is 
done  by  inclosing  the  site  of  the  foundation  with  a  water- 
tight wall  of  timber,  from  within  which  the  water  can  be 
pumped  out  by  steam  power  or  otherwise.  Sometimes,  in 
shallow  water,  it  is  sufficient  to  drive  a  single  row  of  piles 
only,  the  outside  being  protected  with  clay,  as  shown  in  fig. 
5  ;  but  in  deep  water  two  or  even  four  rows  of  piles  will  be 


Fig,  5. 


required,  the  space  between  them  being  filled  in  with  well- 
rammed  fuddkj  so  as  to  form  a  solid  water-tight  mass. 
(See  fig  6.)    The  great  difficulties  in  the  construction  of  a 


Fig.  6. 


cofferdam  are — 1st,  to  keep  it  water-tight  ;  and,  2nd,  to 
support  the  sides  against  the  pressure  of  the  water  outside, 
which  in  tidal  waters  is  sometimes  so  great  as  to  render  it 
necessary  to  allow  a  dam  to  fill  to  prevent  its  being  crushed. 


ART  OF  BUILDING. 


25 


24.  In  order  to  save  timber,  and  to  avoid  the  difficulty  of 
keeping  out  the  bottom  springs,  it  has  been  proposed  by  a 
French  engineer,  after  driving  the  outer  row,  to  dredge  out 
the  area  thus  inclosed,  and  fill  it  up  to  a  certain  height  with 
beton.  The  cofferdam  is  then  to  be  completed  by  driving  an 
inner  row  of  piles  resting  on  the  beton,  and  puddhng  between 
the  two  rows  in  the  usual  manner  ;  and  the  masonry  is 
carried  up  on  the  beton  foundation  thus  prepared.  This  con- 
struction is  shown  in  fig.  7. 


Fzg.  7. 


25.  Concrete  is  a  valuable  material  when  applied  in  a 
proper  manner,  viz.,  in  underground  works  where  it  is  con- 
fined on  all  sides,  and  is,  consequently,  subjected  to  little 
cross  strain  ;  but  it  is  not  fit  to  be  used  above  ground  as  a 
substitute  for  masonry,  and  will  not  bear  exposure  to  water. 

26.  Concrete  is  made  of  gravel,  sand,  and  ground  lime, 
mixed  together  with  water  ;  the  slaking  of  the  lime  taking 
place  whilst  in  contact  with  the  sand  and  gravel.  It  is 
difficult  to  give  any  definite  proportions  for  the  several 
ingredients,  but  the  principle  to  be  followed  in  proportioning 
the  several  quantities  of  sand  and  stones  should  be  to  form 
as  much  as  possible  a  solid  mass,  for  which  purpose  it  is  desir- 
able that  the  stones  should  be  of  various  sizes,  and  angular 
rather  than  rounded.  The  common  material  is  unscreened 
gravel,  containing  a  considerable  portion  of  sand  and  large 
and  small  pebbles,  but  small  irregular  fragments  of  broken 


26 


RUDIMENTS  OF  THE 


stone,  granite  chippings,  and  the  like,  are  of  great  service, 
as  they  interlace  each  other  and  bind  the  mass  together. 
The  proportion  of  lime  to  sand  should  be  such  as  is  best 
suited  to  form  a  cement  to  connect  the  stones.  This  must 
depend  in  a  great  measure  on  the  quality  of  the  lime  used  ; 
the  pure  limes  requiring  a  great  proportion  of  sand,  whilst 
the  stone  limes,  and  those  containing  alumina,  silica,  and 
metallic  oxides,  require  a  much  smaller  proportion. 

2T.  The  lime  and  gravel  should  be  thoroughly  incorporated 
by  being  repeatedly  turned  over  with  shovels,  sufficient  water 
being  added  to  ensure  the  thorough  slaking  of  the  lime  with- 
out drowning  it.  Concrete  should  not  be  thrown  into  water, 
because  ordinary  stone  lime  will  not  set  under  such  circum- 
stances ;  and  it  should  be  carefully  protected  from  any  wash 
or  run  of  water,  which  would  have  the  effect  of  washing  out 
the  lime,  and  leaving  the  concrete  in  the  state  of  loose 
gravel.  Concrete  made  in  the  way  just  described  swells 
slightly  before  setting,  from  the  expansion  due  to  the  slaking 
of  the  lime,  and  does  not  return  to  its  original  bulk.  This 
property  makes  it  valuable  for  underpinning  foundations  and 
similar  purposes. 

28.  Beton. — Beton  may  be  considered  as  hydraulic  con- 
crete ;  that  is,  concrete  made  with  hydraulic  lime  ;  and  is 
chiefly  used  in  submarine  works,  as  a  substitute  for  masonry, 
in  situations  where  the  bottom  cannot  be  laid  dry.  It  differs 
from  ordinary  concrete  inasmuch  as  the  lime  must  be  slaked 
before  mixing  with  the  other  ingredients,  and  it  is  usual  to 
make  the  lime  and  sand  into  mortar  before  adding  the  stones. 
Concrete  also  is  used  hot,  whilst  beton  is  allowed  to  stand 
before  being  used,  in  order  to  ensure  the  perfect  slaking  of 
every  particle  of  lime.  Belidor  directs  that  the  mortar  shall 
first  be  made,  with  pozzuolana,  sand,  and  quicklime. 
When  the  mortar  is  thoroughly  mixed,  the  stones  are  to  be 
thrown  in  (not  larger  than  a  hen^s  egg),  and  also  iron  dross 
well  pounded  ;  the  whole  is  then  to  be  thoroughly  incorpor- 


ART  OF  BUILDING. 


27 


ated,  and  left  for  twenty-four  hours, 
be  as  follows  : — 

Pozzuolana    .  12 

Sand   6 

Good  quicklime  9 
Small  stones  .  13 
Ground  slag  .  3 

43 

The  beton  is  to  be  lowered  into  the  water  in  a  box,  with 
a  bottom  so  constructed  that  it  can  be  opened,  and  its  con- 
tents discharged,  by  pulling  a  cord,  so  as  to  deposit  the  beton 
on  the  bottom  without  having  to  fall  through  a  depth  of 
water,  w^iich  might  wash  away  the  lime.  For  the  same 
reason  it  is  necessary,  before  commencing,  to  lay  the  beton, 
to  surround  the  site  with  sheet-piling,  to  protect  it  from  the 
action  of  the  water,  and  to  guard  against  the  danger  of  the 
softer  portions  of  the  work  being  carried  away  by  tempests 
before  they  become  consolidated. 

29.  The  ordinary  method  of  using  beton  on  the  Continent 
is  in  alternate  layers  of  beton  and  rubble  stone.  A  layer  of 
beton,  about  a  foot  in  thickness,  is  first  spread  over  the  whole 
area  of  the  foundation,  and  on  this  is  laid  a  stratum  of 
rubble,  which,  sinking  into  the  soft  beton,  becomes  thoroughly 
incorporated  with  it.  On  this  is  laid  another  layer  of  beton, 
followed  by  another  course  of  rubble  ;  this  system  being 
pursued  until  the  work  reaches  the  intended  height. 

30.  Pile-driving. — The  usual  method  of  pile-driving  is  by 
a  succession  of  blows  given  by  a  heavy  block  of  w^ood  or 
iron  (called  a  monkey,  or  ram,  or  tup),  which  is  raised  by  a 
rope  or  chain  passed  over  a  pulley  fixed  at  the  top  of  an  up- 
right frame  of  timber,  and  allowed  to  fall  freely  on  the  head 
of  the  pile  to  be  driven.  There  are  a  large  number  qf  pHe^ 
drivers  of  different  styles  in  use.  The  one  most  commonly 
used  in  the  United  States  is  Captain  Gramas. 


The  proportions  are  to 
parts. 

?7 


28 


RUDIMENTS  OF  THE 


31.  In  selecting  timber  for  piles,  care  should  be  taken  to 
choose  that  which  is  straight-grained  and  free  from  knots 
and  ring  shakes.  Larch,  fir,  beech,  and  oak,  are  the  woods 
most  esteemed.  In  situations  exposed  to  the  worm,  there  is 
little  difference  in  the  durability  of  the  best  and  the  worst 
timber,  if  unprepared,  and,  therefore,  it  is  always  safest  to 
use  some  preserving  process. 

32.  Piles  which  have  to  be  driven  through  hard  ground 
require  to  be  ru7igj  that  is,  to  have  an  iron  hoop  fixed  tightly 
on  their  heads,  to  prevent  them  from  splitting,  and  also  to 
be  shod  with  iron  shoes  ;  the  shoes  may  be  of  wrought  or  of 
cast  iron.  For  single  piles  the  point  of  the  shoe  is  placed  in 
the  centre  of  the  pile  ;  but  for  sheet-piling,  the  shoes  are 
made  not  with  a  point,  but  with  an  edge,  which  is  not  level, 
but  slightly  inclined,  so  as  in  driving  to  give  the  pile  a  drift 
towards  the  pile  last  driven,  by  which  means  a  close  contact 
is  ensured.  Great  care  is  required,  in  shoeing  a  pile,  to  en- 
sure that  the  shoe  is  driven  perfectly  home.  The  advantage 
of  a  cast-iron  shoe  is,  that  the  inside  can  be  formed  with  a 
square  abutment  on  which  the  pile  rests,  whilst  a  wr ought- 
iron  shoe  has  to  be  driven  up  until  the  toe  of  the  pile  is 
wedged  tight,  and,  as  the  force  with  which  the  pile  is  driven 
into  the  ground  greatly  exceeds  that  with  which  the  shoe  is 
driven  on  the  pile,  it  will  often  happen  that  the  shoe  will 
burst  open,  and  allow  the  point  of  the  pile  to  be  crushed  be- 
fore it  is  down  to*its  full  depth. 

33.  Sheeting  piles  should  be  carefully  fitted  to  each  other 
before  driving,  otherwise  they  cannot  be  expected  to  come 
in  close  contact  when  driven  In  some  few  cases  it  is  worth 
while  to  groove  and  tongue  the  edges,  but  this  is  seldom 
done,  and  if  the  piles  are  perfectly  parallel  and  truly  driven, 
the  swelling  of  the  wood  when  exposed  to  moisture  will 
generally  secure  a  tight  joint. 

34.  As  a  general  rule,  broken  timber,  that  is,  timber  cut 
out  of  larger  balks,  should  be  avoided.  A  10-in.  stick  of 
Swedish  timber  will  drive  better  and  with  less  risk  of  split- 


ART  OF  BUILDING. 


29 


ing  than  a  quarter  of  a  20-in.  balk  of  best  Dantzic.  If 
piles  must  be  cut  from  large  balks,  the  heart  of  the  wood 
should,  if  possible,  be  left  in  the  centre  of  the  pile. 

35.  In  driving  sheet-piling,  the  piles  are  kept  in  their  pro- 
per position  by  horizontal  pieces  of  timber  called  wales ^  which 
are  fixed  to  guide  piles  previously  driven.  In  driving  coffer- 
dams and  similar  works,  the  wales  are  seldom  placed  below 
the  water-line,  but  this  may  be  done  with  great  benefit  by 
attaching  the  wales  to  hoops  dropped  over  the  heads  of  the 
guide  piles,  and  pushed  down  as  low  as  the  ground  will  per- 
mit. In  driving  into  or  through  a  hard  stratum,  it  is  de- 
sirable that  the  auger  should  precede  the  driving,  as  it  will 
save  much  time,  and  much  injury  to  the  piles  ;  and  in  all 
cases  where  a  hard-bearing  stratum  has  to  be  reached  at  a 
variable  depth,  the  boring-rod  should  be  used  to  ascertain 
the  length  of  pile  required,  as  nothing  is  more  vexatious  than 
finding  a  pile  a  few  inches  too  short  when  driven,  or,  on  the 
other  hand,  having  to  cut  ofT  5  or  6  ft.  of  good  timber,  which 
must  be  needlessly  wasted. 

36.  Many  writers  have  endeavored  to  lay  down  rules  for 
calculating  the  effect  of  a  given  blow  in  sinking  a  pile,  but 
investigations  of  this  kind  are  of  little  practical  value,  because 
we  can  never  be  in  possession  of  sufficient  data  to  enable  us 
to  obtain  even  an  approximate  result.  The  effect  of  each 
blow  on  the  pile  will  depend  on  the  force  of  the  blow,  the 
velocity  of  the  ram,  the  relative  weights  of  the  ram  and  the 
pile,  the  elasticity  of  the  pile  head,  and  the  resistance  offered 
by  the  ground  through  which  the  pile  is  passing,  and  as  we 
never  can  ascertain  the  two  last-named  conditions  with  any 
certainty,  any  calculations  in  which  they  are  only  assumed 
must  of  necessity  be  mere  conjectures. 

31.  Piles  driven  for  temporary  purposes  are,  at  the  com- 
pletion of  their  term  of  service,  either  drawn  for  the  value  of 
the  timber  and  iron  shoes,  or  cut  off  at  the  level  of  the 
ground  if  they  are  in  situations  where  the  drawing  of  the 
piles  might  cause  any  risk  to  the  adjacent  work.  When 


30 


RUDIMENTS  OF  THE 


sheet-piling  has  been  driven  round  the  foundations  of  any 
work,  as  in  forming  a  cofferdam  round  the  pier  of  a  bridge, 
there  will  always  be,  in  the  event  of  its  being  drawn,  the 
risk  of  the  ground  settling  down  to  fill  up  the  vacancy  thereby 
occasioned  ;  but  in  clay  or  marl  soils  this  is  not  the  greatest 
danger,  for  the  water  scours  out  and  enlarges  the  race  thus 
formed,  and  the  bottom  speedily  becomes  broken  up,  nearly 
to  the  depth  to  which  the  piles  were  driven.  As  a  general 
rule,  therefore,  it  may  be  laid  down,  that  piles  in  such  situa- 
tions should  never  be  drawn,  but  should  be  cut  off  at  the 
level  of  the  ground,  nnd  this  may  be  done  in  various  ways. 
1st.  By  common  means,  the  men  working  in  a  diving  bell, 
or  with  diving-helmets.  2d.  By  machinery  especially  con- 
structed for  the  purpose.  3d.  In  the  case  of  cofferdams,  by 
cutting  the  piles  nearly  through  from  the  inside  with  the 
adze,  leaving  the  water  on  the  outside  of  the  piles  to  com- 
plete the  operation  on  the  removal  of  the  strutting. 

38.  There  are  many  cases,  however,  in  which  it  becomes 
necessary  to  draw  piles,  and  the  modes  in  which  this  may  be 
done  are  almost  infinite.  The  common  plan,  where  the  situ- 
ation will  admit  of  it,  is  to  make  use  of  a  balk  of  timber  as  a 
lever,  one  end  of  which  is  shackled  to  the  head  of  the  pile, 
whilst  to  the  other  end  is  applied  such  power  as  can  most 
readily  be  obtained. 

39.  A  very  simple  method  of  drawing  piles  is  by  means  of 
a  powerful  screw,  of  which  one  end  is  hooked  to  a  shackle 
passing  round  the  head  of  the  pile,  whilst  the  other  passes 
through  a  cross-head,  resting  firmly  on  temporary  supports 
placed  on  each  side  of  the  pile. 

40.  Cofferdams. — A  cofferdam  may  be  described  as  a 
water-tight  wall,  constructed  round  the  site  of  any  work,  for 
the  purpose  of  laying  dry  the  bottom  by  pumping  out  the 
water  from  the  area  thus  enclosed.  In  some  situations,  this 
may  be  effected  by  earthern  dams,  by  bags  of  clay  piles  ou 
each  other,  or  by  rough  caissons,  without  top  or  bottom, 


ART  OF  BUILDING. 


81 


filled  with  clay,  and  sunk  in  line  round  the  space  to  be  en- 
closed ;  but  in  the  majority  of  cases,  the  method  is  to  drive 
two  or  more  rows  of  close  piling,  and  to  fill  up  the  space  be- 
tween them  with  clay  puddle. 

41.  Cofferdams  are  sometimes  formed,  in  shallow  water, 
with  a  single  row  of  sheet-piling  ;  but  this  is  very  precarious 
work,  as,  unless  the  piles  are  fitted  together  with  great 
truth,  it  is  impossible  to  keep  the  joints  close,  and  to  prevent 
leakage.  A  single  row  of  sheet-piling  may,  however,  be 
often  used  with  great  advantage  as  a  protection  and  support 
in  front  of  .an  earthen  dam,  and  this  is  a  very  economical 
and  satisfactory  method  of  proceeding  where  there  is  no 
depth  of  water. 

42.  Cofferdams  are  subject  to  heavy  external  pressure 
from  the  water  round  them,  w^hich  would  crush  them 
in,  were  they  not  very  firmly  strutted.  In  cofferdams 
inclosing  a  small  area,  as,  for  instance,  the  site  of  the  pier  of 
a  bridge,  the  strutting  is  placed  from  side  to  side,  in  the 
manner  that  will  give  the  greatest  facility  for  carrying  on  the 
work,  the  struts  being  gradually  removed  as  the  latter  pro- 
ceeds. 

In  constructing  dams  in  front  of  a  wharf  wall,  or  similar 
work,  the  strutting  requires  to  be  effected  in  a  different  man- 
ner, and  the  plan  usually  adopted  is  to  form  a  series  of  but- 
tresses, or  counterforts,  at  short  intervals,  from  which  the 
intermediate  portions  of  the  dam  can  be  strutted  with  raking, 
horizontal  struts.  The  strength  given  to  these  counterforts 
must,  of  course,  depend  on  the  amount  of  pressure  to  come 
on  the  dam. 

•  43.  In  rivers  subject  to  heavy  freshets  it  is  common,  in 
constructing  cofferdams,  to  keep  the  top  of  the  dams  below 
the  flood  level,  as  it  is  generally  less  expensive  to  pump  out 
the  water  from  the  interior  of  the  dam  occasionally,  than  to 
construct  and  maintain  a  dam  which  should  sustain  the 
pressure  of  the  flood  waters  ;  and  it  is  always  advisable  to 
provide  every  dam  with  a  sluice,  by  mean  of  which  the  water 


82 


RUDIMENTS  OF  THE 


can  be  admitted,  if  there  is  any  fear  of  injury  from  a  sudden 
freshet  or  from  any  other  cause.  In  tidal  waters  the  operation 
of  closing  a  dam  is  sometimes  ratlier  hazardous  (unless  it 
can  be  performed  at  low  water),  from  the  tide  falling  out- 
side, without  the  dead  w^ater  inside  being  able  to  escape 
sufficiently  quick  through  the  sluices  to  maintain  an  equili- 
brium ;  and,  unless  the  piles  and  puddle  wall  are  sufficiently 
strong  to  resist  this  outward  pressure,  the  work  will  be 
violently  strained,  and  often  permanently  injured.  When 
the  site  to  be  inclosed  is  above  the  level  of  low  water,  half- 
iide  dams  are  sometimes  resorted  to.  A  half-tide  dam  is  one 
which  is  covered  and  filled  at  every  tide,  and  emptied  by 
sluices  at  low  water,  the  available  working  hours  lasting  from 
the  time  the  bottom  runs  dry  until  the  flood  tide  reaches  the 
top  of  the  dam. 

44.  The  principal  difficulties  in  the  construction  of  coffer- 
dams may  be  thus  briefly  stated  : — 

1st.  To  obtain  a  firm  foothold  for  the  piles,  which,  in  either 
Tock  or  mud,  is  a  matter  of  great  difficulty. 

2d.  To  prevent  leakage  between  the  surface  of  the  ground 
and  the  bottom  of  the  puddle. 

8d.  To  prevent  leakage  through  the  puddle  wall* 

4th.  To  keep  out  the  bottom  springs. 

HETAINING  WALLS. 

45,  The  name  of  retainhig  wall  is  applied  generally  to  all 
walls  built  to  support  a  mass  of  earth  in  an  upright  or  nearly 
upright  position  ;  but  the  term  is,  strictly  speaking,  restricted 
to  walls  built  to  retain  an  artificial  bank,  those  erected  to 
sustain  the  face  of  the  solid  ground  being  called  hrm&t  wails, 
(See  fig.  8. 


ART  OF  BUILDING. 


33 


Fig,  8. 


46.  Retaining  Walls. — Many  rules  have  been  given  by 
different  writers  for  calculating  the  thrust  which  a  bank  of 
earth  exerts  against  a  retaining  wall,  and  for  determining  the 
form  of  wall  which  affords  the  greatest  resistance  with  the 
least  amount  of  material.  The  application  of  these  rules  to 
practice  is,  however,  extremely  difficult,  because  we  have  no 
means  of  ascertaining  the  exact  manner  in  which  earth  acts 
against  a  wall  ;  and  they  are,  therefore,  of  little  value  *except 
in  determining  the  general  principles  on  which  the  stability 
of  these  constructions  depends. 

4Y.  The  calculation  of  the  stability  of  a  retaining  wall 
divides  itself  into  two  parts  : 

1st.  The  thrust  of  the  earth  to  be  supported. 

2d.  The  resistance  of  the  wall. 

48.  Definitions  (see  fig.  9.) — The  line  of  rupture  is  that 
along  which  separation  takes  place  in  case  of  a  slip  of 


earth.  The  slope  which  the  earth  would  assume,  if  left  to- 
tally unsupported,  is  called  the  natural  slope,  and  it  has  been 

3 


Fig.  9. 


CEHTRE  OF  PRESSURE. 


34 


RUDIMENTS  OF  THE 


found  that  the  line  of  rupture  generally  divides  the  angle 
formed  by  the  natural  slope  and  the  back  of  the  wall  into 
nearly  equal  parts. 

The  centre  of  pressure  is  that  point  in  the  back  of  the  wall 
above  and  below  which  there  is  an  equal  amount  of  pressure  ; 
and  this  has  been  found  by  experiment  and  calculation  to  be 
at  two-.thirds  of  the  vertical  height  of  the  wall  from  its  top. 

The  wall  is  assumed  to  be  a  solid  mass,  incapable  of 
sliding  forward,  and  giving  way  only  by  turning  over  on  its 
front  edge  as  a  fulcrum.  In  the  annexed  diagrams  the 
foundations  of  the  walls  have,  in  all  cases,  been  omitted,  to 
simplify  the  subject  as  much  as  possible.  The  term  slope  in 
the  following  investigation  is  used  as  synonymous  with  the 
expression  line  of  rupture, 

49.  Amount  and  Direction  of  the  Thrust. — There  are  two 
ways  in  which  this  may  be  calculated  : — 1st,  By  considering 
the  earth  as  a  solid  mass  sliding  down  an  inclined  plane,  all 
slipping  between  the  earth  and  the  back  of  the  wall  being 
prevented  by  friction.  This  gives  the  minimum  thrust  of  the 
earth.  2nd,  By  assuming  the  particles  of  earth  to  have  so 
little  cohesion,  that  there  is  no  friction  either  on  the  slope  or 
against  the  back  of  the  wall.  This  method  of  calculation 
gives  the  maximum  thrust. 

The  real  thrust  of  any  bank  will  probably  be  somewhere 
between  the  two,  depending  on  a  variety  of  conditions  which 
it  is  impossible  to  reduce  to  calculation  ;  for,  although  we 
may  by  actual  experiments  with  sand,  gravel,  and  earths  of 
different  kinds,  obtain  data  whence  to  calculate  the  thrust 
exerted  by  them  in  a  perfectly  dry  state,  another  point  must 
be  attended  to  when  we  attempt  to  reduce  these  results  to 
practice,  viz.,  the  action  of  water,  which,  by  destroying  the 
cohesion  of  the  particles  of  earth,  brings  the  mass  of  material 
behind  the  wall  into  a  semi-fluid  state,  rendering  its  action 
more  or  less  similar  to  that  of  a  fluid  according  to  the  degree 
of  saturation. 


ART  OF  BUILDING. 


85 


The  tendency  to  slip  will  also  very  greatly  depend  on  the 
manner  in  which  the  material  is  filled  against  the  wall.  If 
the  ground  be  benched  out  (see  fig.  8,)  and  the  earth  well 
punned  in  layers  inclined /ro?^^  the  wall,  the  pressure  will  be 
very  trifling,  provided  only  that  attention  be  paid  to  surface 
and  back  drainage.  If,  on  the  other  hand,  the  bank  be  tip- 
ped in  the  usual  manner  in  layers  sloping  towards  the  wall, 
the  full  pressure  of  the  earth  will  be  exerted  against  it,  and 
it  must  be  made  of  corresponding  strength, 

60.  Calculation  of  Miniinum  Thrust. — The  weight  of  the 
prism  of  earth  represented  by  the  triangle  ABC,  fig.  9, 


Fig,  10. 


the  earth,  5,  we  shall  have  TV 


will  be  directly  as  the  breadth  AC^ 
the  height  being  constant ;  and  the 
inclination  of  B  C  remaining  con- 
stant, but  the  height  varying,^  the 
weight  will  be  as  the  square  of  the 
height.  If,  therefore,  we  call  the 
weight  of  the  prism  ABC,  W, 
the  breadth  AC,  6,  the  height 
AB,  h,  and  the  specific  gravity  of 
h  hs 


If  we  call  the 


thrust  of  W  in  the  direction  of  the  slope  W,  then  (neglect- 
ing friction, )  on  the  principle  of  the  inclined  plane,  W  will 
be  to  W  as  the  length  of  the  incline  is  to  its  height  ;  or, 
calling  the  length  B  C,  then 


Z  :  A  :  :  W  :  W : 


I 


2Z 


*  The  value  of  W'  here  given  will  increase  with  the  length,  of  A  C  in  a  constantly 
decreasing  ratio,  never  exceeding  —  supposing  the  back  of  the  wall  to  be  upright. 

2 

But  in  practice  the  friction  must  always  be  taken  into  consideration  ;  and,  as  this 
increases  directly  as  A  C,  there  wiU  be  a  limit  at  which  the  thrust  and  the  resist- 
ance balance  each  other,  this  limit  being  the  natural  slope  ;  and,  as  the  thrust  and 
the  resistance  increase  with  the  length  of  A  C  in  different  ratios,  there  will  be  a 
point  at  which  the  effective  thrust  is  greatest,  or,  in  other  words,  a  slope  of  maxi- 
mum  thrust  v/hich  determines  the  position  of  the  line  of  rupture. 


RUDIMENTS  OF  THE 


The  effect  of  the  weight  of  the  prism  A  B  C  to  oyertnm  the 
wall  will  be  as  W  multiplied  by  the  leyerage  E  fig.  10, 
found  by  letting  fall  the  perpendicular  E  from  the  front 
edge  of  the  wallj,  upon  D  F,  drawn  through  the  centre  of 
pressure  in  a  direction  parallel  to  the  slope.  When  D  F 
passes  through  E,  then  E  F  =  0,  and  the  thrust  has  no  ten< 
dencj  to  overturn  the  wall  ;  and  when  D  P  falls  within  the 
base  of  the  wall^  E  F  becomes  a  negatiye  quantity^  the  thrust 
increasing  its  stability.  Calling  the  overturning  thrust  T, 
we  have 

5^2^  4- EF, 

T  —  WXBF^  . 

21 

the  value  of  E  ¥^  depending  on  the  inclination  of  the  slope, 
and  the  width  of  the  base  of  the  wall. 

51.  Calculation  of  Maximum  Thrust.— ii  we  consider  the 
moving  mass  to  slide  freely  down  the  slope,  and  the  friction 
between  the  earth  and  the  back  of  the  wall  to  be  so  slight 
as  to  be  inappreciable,  then  the  prism  ABC  will  act  as  a 
wedge,  with  a  pressure  perpendicular  to  the  back  of  the 
wall;  which  will  be  the  same  whatever  the  inclination  of  B 
C,  the  height  and  inclination  of  the  back  of  the  wall  being 
constant,  and  as  the  square  of  the  height  where  the  height 
varies,  the  pressure  being  the  least  when  the  back  of  the 
wall  is  vertical ;  for  calling  the  pressure  P,  and  drawing 
AT,  fig.  11,  perpendicular  to  B  C,  we  have,  on  the  princij  le 
of  the  wedge, 

W'X  AB  5A2^XAB 

AI:AB::W'  :  P  =  — =—  

AI  2/XAI 

and  by  construction  hh^^^l  A  I,  as  they  are  each  equa)  fco 


*  EF=-  X  (  -  -  EB  1  and 

5       ii  (h      \  b  m  s  hfh 

T=W'XEF=^-  X-  EB  r  X 


ART  OF  BUILDING. 


3t 


twice  the  area  of  triangle  ABC;  therefore,  by  substitution, 
lAlhsXAB     hsX  AB 


2/AI  2 
The  effect  of  the  prism  A  B  C  to  overturn  the  wall  will  be 
P  multiplied  by  the  leverage  EF*,  which  will  be  found  by 
drawing  DF,  fig  13,  at  right  angles  to  the  back  of  the  wall 


i/ 

through  the  centre  of  pressure,  and  making  E  F  perpendicular 
to  it ;  then  calling  the  overturning  thrust,  as  before,  T, 

ABXhsXEF 
T  =  PXEF=  . 


When  D  F  passes  through  E,  then  E  F  =  0,  and  the  thrust 
has  no  tendency  to  overturn  the  wall  ;  and,  if  D  F  falls  within 
the  base,  the  thrust  will  increase  its  stability.  When  the 
back  of  the  wall  is  vertical,  then 

AB  —  h  and  EF  =  — and  T  =  — . 

3  6 

*  Calling  the  angle  X  A  B  =  ^ 
AB      EB.AX  h 

EF  =  1  =    cosec.  ^     E  B  cos.  d 

3   ~     AB         3  — 


And  T  =  P  X  E  F  : 

hs 


AB.hs 


2 

AB2 


X 


EB 


AB  EB.AXX 
3   ^     AB  / 


.AX^ 


Tlie  poRitivo  sign  \fi  to  be  used  when  tlie  back  of  the  wall  leans  backwards  ;  th« 
negativo,  when  it  leans  forwards. 


38 


RUDIMENTS  OF  THE 


52.  These  results  show  that,  where  the  friction  of  the 
earth  against  the  slope  and  the  back  of  the  wall  is  destroyed 
by  the  filtration  of  water,  the  action  of  the  earth  will  be 
precisely  similar  to  that  of  a  column  of  water  of  the  height 
of  the  wall.  The  pressure  upon  the  side  of  any  vessel  is  the 
half  of  the  pressure  that  would  take  place  upon  the  bottom 
if  of  the  same  area.  Now,  calling  the  specific  gravity  of  the 
water  s,  the  pressure  upon  the  bottom,  supposing  its  length 
to  be  A  B,  would  be  ^  5  A  B  ;  therefore  the  pressure  upon 
the  side  will  be  A  .9  A  B  A  5  A  B.E  F 

 ;  andT=:PXEri=:  . 

2 

And,  where  the  back  of  the  wall  is  vertical,  then 

h 

AB  =  k  and  E  F  =  -  as  above.  Therefore 
3 

p  andTzrz  — X-  =  — ; 

2  2     3  6 

which  results  are  precisely  the  same  as  those  arrived  at 
above. 

53.  Resistance  of  the  Wall. — Considering  the  wall  as  a 
solid  mass,  the  effect  of  its  weight  to  resist  an  overturning 
thrust  will  be  directly  as  the  horizontal  distance  E  H  from 
its  front  edge  to  a  vertical  line  drawn  through  G,  the  centre 
of  gravity  of  the  wall,  fig.  13  ;  or,  calling  the  resistance  R, 
and  the  weight  of  the  wall  then  R  =  ^^;XEII.  EH  will 
be  directly  as  E  B,  the  proportions  of  the  wall  being  con- 
stant ;  therefore  a  wall  of  triangular  section  will  afford  more 
resistance  than  a  rectangular  one  of  equal  sectional  area, 
the  base  of  a  triangle  being  twice  that  of  a  rectangle  of 
equal  height  and  area. 

If  the  wall  be  built  with  a  curved  concave  batter,  fig.  14, 
E  H  will  be  still  greater  than  in  the  case  of  a  triangular 
wall  of  equal  sectional  area  ;  and,  if  the  wall  were  one  solid 


ART  OF  BUILDING. 


89 


Fig.  13. 


A 


b 


mass  incapable  of  fracture, 
this  form  would  offer  more  re- 
sistance than  the  triangular. 
But,  as  this  is  not  the  case, 
we  may  consider  any  portion 
of  the  wall  cut  off  from  the 
bottom  by  a  level  line  to 
be  a  distinct  wall  resting  upon 
the  lower  part  as  a  foundation. 


Imagine  A  e  5  to  be  a  complete  wall  capable  of  turning  upon 
e  as  a  fulcrum.  The  resistance  would  be  considerably  less 
than  that  of  the  corresponding  portion  of  a  triangular  wall. 
In  the  case  of  a  triangular  wall,  the  proportions  of  the 
resistance  to  the  thrust  will  be  the  same  throughout  its 
height.  In  the  case  of  a  rectangular  one,  the  resistance  will 
bear  a  greater  proportion  to  the  thrust,  the  greater  the  dis- 
tance from  the  bottom.  In  the  case  of  a  wall  with  a  con- 
cave curved  batter,  the  reverse  of  this  takes  place. 

The  value  of  E  H  will  be  greatest  when  E  H  E  B,  the 
wall  will  be  then  exactly  balanced  on  H  ;  but  in  practice 
this  limit  should  never  be  reached,  for  fear  the  wall  should 
become  crippled  by  depending  on  the  earth  for  support.  The 
value  of  E  H  will  be  least  when  H  coincides  with  E,  which 
opposite  limit  also  is  never  reached  in  practice — ^for  obvious 
reasons — as  the  wall  would  in  this  case  overhang  its  base, 
and  be  on  the  point  of  falling  forward. 

54.  The  increased  leverage  is  not  the  only  advantage 
gained  by  the  triangular  form  of  wall.  In  the  foregoing 
investigation,  we  have  considered  the  wall  as  a  solid  mass 
turning  on  its  front  edge.  Kow^,  practically,  the  difficulty  is 
not  so  much  to  keep  the  wall  from  overturning  as  to  prevent 
the  courses  from  sliding  on  each  other. 

In  an  upright  wall,  built  in  horizontal  courses,  the  chief 
resistance  to  sliding  arises  from  the  adhesion  of  the  mortar ; 
but,  if  the  wall  be  built  with  a  sloping  or  battering  face,  the 
beds  of  the  courses  being  inclined  to  the  horizon,  the  resist- 


40 


RUDIMENTS  OF  THE 


ance  to  the  thrust  of  the  bank  is  increased  in  propor- 
tion to  the  tendency  of  the  courses  to  shde  down 
towards  the  bank ;  thus  rendering  the  adhesion  of  the 
mortar  merely  an  additional  security.  The  importance 
of  making  the  resistance  independent  of  the  adhesion 
of  the  mortar  is  obviously  very  great,  as  it  would  otherwise 
be  necessary  to  delay  backing  up  a  wall  until  the 
mortar  were  thoroughly  set,  which  might  require  several 
months. 

55.  The  exact  determination  of  the  thrust  which  will  be 
exerted  against  a  wall  of  given  height  is  not  possible  in 
practice  ;  because  the  thrust  depends  on  the  cohesion 
of  the  earth,  the  dryness  of  the  material,  the  mode  of 
backing  up  the  wall,  and  other  conditions  which  we 
have  no  means  of  ascertaining.  Experience  has,  however, 
shown  that  the  base  of  the  wall  should  not  be  less  than 
one-fourth,  and  the  batter  or  slope  not  less  than  one- 
sixth  of  the  vertical  height,  w^herever  the  case  is  at  all 
doubtful. 

56.  The  results  of  the  above  investigation  are  illustrated 
in  figures  14,  15,  16,  17,  and  18,  which  show  the  relative 

Fig.  14.  Fig.  15. 


sectional  areas  of  walls  of  different  shapes,  that  would  be 
required  to  resist  the  pressure  of  a  bank  of  earth  12  feet 
high. 


ART  OF  BrjILDING. 


41 


Fig.  16.  Fig.  17. 


The  first  three  examples  are  calculated  to  resist  the  maxi- 
mum, and  the  fourth,  the  minimum,  thrust  ;  whilst  the  last 
figure  shows  the  modified  form  usually  adopted  in  practice. 

57.  It  is  sometimes  necessary  in  soft  ground  to  protect  the 
toe  or  front  edge  of  a  retaining  wall  with  sheet  pihng,  to  pre- 
vent it  from  being  forced  forward  ;  this  is  shown  in  fig.  8. 

58.  Counterforts. — Retaining  walls  are  often  built  with 
counterforts,  or  buttresses,  at  short  distances  apart,  which 
allow  of  the  general  section  of  the  wall  being  made  lighter 
than  would  otherwise  be  the  case.  The  principle  on  which 
these  counterforts  are  generally  built  is,  however,  very  de- 
fective, as  they  are  usually  placed  behind  the  wall,  which 
frequently  becomes  torn  from  them  by  the  pressure  4)f  the 
earth.  The  strength  of  any  retaining  wall  would,  however, 
be  greatly  increased  were  it  built  as  a  series  of  arches,  abut- 


42 


RUDIMENTS  OF  THE 


ting  on  long  and  thin  buttresses  ;  but  the  loss  of  space  that 
would  attend  this  mode  of  construction  has  effectually  pre- 
vented its  adoption  except  in  a  few  instances. 

69.  Breast  Walls. — Where  the  ground  to  be  supported  is 
firm,  and  the  strata  are  horizontal,  the  office  of  a  breast  wall 
is  more  to  protect,  than  to  sustain  the  earth.  It  should  be 
borne  in  mind  that  a  trifling  force,  skilfully  applied  to  un- 
broken ground,  will  keep  in  its  place  a  mass  of  material 
which,  if  once  allowed  to  move,  would  crush  a  heavy  wall ; 
and,  therefore,  great  care  should  be  taken  not  to  expose  the 
newly  opened  ground  to  the  influence  of  air  and  wet  for  a 
moment  longer  than  is  requisite  for  sound  work,  and  to  avoid 
leaving  the  smallest  space  for  motion  between  the  back  of 
the  wall  and  the  ground. 

60.  The  strength  of  a  breast  wall  must  be  proportionately 
increased  when  the  strata  to  be  supported  incline  towards 
the  wall,  as  in  fig.  19  :  where  they  incline  from  it,  the  wall 
need  be  little  more  than  a  thin  facing  to  protect  the  ground 
from  disintegration. 


Fig  19. 


61.  The  preservation  of  the  natural  drainage  is  one  of  the 
most  important  points  to  be  attended  to  in  the  erection  of 
breast  walls,  as  upon  this  their  stability  in  a  great  measure 
depeijfls.  No  rule  can  be  given  for  the  best  manner  of  doing 
this  ;  it  must  be  a  matter  for  attentive  consideration  in  each 
particular  case. 


ART  OF  BUILDING. 


43 


ARCHES. 

62.  An  arch  in  perfect  equilibrium  may  be  considered  as 
a  slightly  elastic  curved  beam,  every  part  of  which  is  in  a 
state  of  compression,  the  pressure  arising  from  the  weight  of 
the  arch  and  its  superincumbent  load  being  transmitted  to 
the  abutments  on  which  it  rests  in  a  curved  line  called  the 
curve  of  equilibrium,  passing  through  the  thickness  of  the 
arch. 

63.  The  wedge-shaped  stones  of  which  a  stone  arch  is 
composed  are  called  the  voussoirs.  The  upper  surface  of  an 
arch  is  called  its  extrados,  and  the  lower  surface  its  intrados 
or  soffit  (see  fig.  20).    Theoretically,  a  stone  arch  might 


Fig,  20. 


give  way  by  the  sliding  of  the  voussoirs  on  each  other  ;  but 
in  practice  the  friction  of  the  material  and  the  adhesion  of 
the  mortar  is  sufficient  to  prevent  this,  and  failure  takes 
place  in  the  case  of  an  overloaded  arch  by  the  voussoirs 
turning  on  their  edges. 

64.  The  curve  of  equilibrium  will  vary  with  the  rise  and 
span  of  the  arch,  the  depth  of  the  arch  stones,  and  the  dis- 
tribution of  the  load,  but  it  will  always  have  this  property, 
namely,  that  the  horizontal  thrust  will  be  the  same  at  every 
part  of  it.    In  order  that  an  arch  may  be  in  perfect  equili- 


44 


RUDIMENTS  OF  THE 


brium,  its  curvature  should  coincide  with  that  of  the  curve 
of  equal  horizontal  thrust ;  if,  from  being  improperly  de- 
signed or  unequally  loaded,  this  latter  curve  approaches 
either  the  intrados  or  the  extrados,  the  voussoirs  will  be 
liable  to  fracture  from  the  pressure  being  thrown  on  a  very 
small  bearing  surface  ;  and  if  it  be  not  contained  within  the 
thickness  of  the  arch,  failure  will  take  place  by  the  joints 
opening,  and  the  voussoirs  turning  on  their  edges. 

65.  The  manner  in  which  the  curve  of  equilibrium  is  af- 
fected by  any  alteration  in  the  load  placed  upon  an  arch  may 
readily  be  seen  by  making  an  experimental  equiUbrated  arch 
with  convex  voussoirs,  as  shown  in  fig.  20.  When  bearing 
its  own  weight  only,  the  points  of  contact  of  the  voussoirs 
will  lie  wholly  in  the  centre  of  the  thickness  of  the  arch  ; 
when  loaded  at  the  crown,  the  points  of  contact  will  ap- 
proach the  extrados  at  the  crown,  and  the  intrados  at  the 
haunches  ;  and,  if  loaded  at  the  haunches,  the  reverse  effect 
will  take  place. 

66.  If  a  chain  be  suspended  at  two  points,  and  allowed  to 
hang  freely  between  them,  the  curve  it  takes  is  the  curve  of 
equilibrium  of  an  arch  of  the  same  span  and  length  on  soffit, 
in  which  the  weights  of  the  voussoirs  correspond  to  the 
weights  of  the  links  of  the  chain,  and  would  be  precisely  the 
same  as  that  marked  out  by  the  points  of  contact  of  the 
curved  voussoirs  of  an  experimental  arch  of  the  same  dimen- 
sions built  as  above  described. 

67.  In  designing  an  arch,  two  methods  of  proceeding  pre- 
sent themselves  :  we  may  either  confine  the  load  to  the 
weight  of  the  arch  itself  or  nearly  so,  and  suit  the  shape  of 
the  arch  to  a  given  curve  of  equilibrium,  or  we  may  design 
the  arch  as  taste  or  circumstances  may  dictate,  and  load  it 
until  the  line  of  resistance  coincides  with  the  curve  thus  de- 
termined upon. 

The  Gothic  vaults  of  the  middle  ages  were,  in  a  great 
,  measure,  constructed  on  the  first  of  these  methods,  being  in 
many  cases  only  a  few  inches  in  thickness,  and  the  curvature 


ART  OF  BUILDING. 


45 


of  the  main  ribs  coinciding  very  nearly  with  their  curves  of 
equal  horizontal  thrust.  We  have  no  means  of  ascertaining 
whether  this  was  the  result  of  calculation  or  experiment ; 
probably  the  latter,  but  the  principle  was  evidently  under- 
stood. 

At  the  present  day,  the  requirements  of  modern  bridge 
building  often  leave  the  architect  little  room  for  choice  in 
the  proportions  of  his  arches,  or  the  height  and  inclinations 
of  the  roadway  they  are  to  carry  ;  and  it  becomes  necessary 
to  calculate  with  care  the  proportion  of  the  load  which  each 
part  of  the  arch  must  sustain,  in  order  that  the  curve  of 
equilibrium  may  coincide  with  the  curvature  of  the  arch. 

68.  The  formulae  for  calculating  the  equilibration  of  an 
arch  are  of  too  intricate  a  nature  to  be  introduced  in  these 
pages  ;  but  the  principles  on  which  they  depend  are  very 
simple. 

Let  it  be  required  to  construct  a  stone  arch  of  a  given 
curvature  to  support  a  level  roadway,  as  shown  in  fig.  20, 
and  to  find  the  weight  with  which  each  course  of  voussoirs 
must  be  loaded  to  bring  the  arch  into  equilibrium. 

Draw  the  centre  line  of  the  arch  to  a  tolerably  large  scale 
in  an  inverted  position  on  a  vertical  plane,  as  a  drawing 
board,  for  instance,  and  from  its  springing  points  a,  sus- 
pend a  fine  silk  thread  of  the  length  of  this  centre  line  strung 
with  balls  of  diameter  and  weight  corresponding  to  the 
thickness  and  weight  of  the  voussoirs  of  the  arch  ;  then, 
from  the  centre  of  each  ball  suspend  such  a  weight  as  will 
bring  the  thread  to  the  curve  marked  on  the  board,  and 
these  weights  will  represent  the  load  which  must  be  placed 
over  the  centre  of  gravity  of  each  of  the  voussoirs,  as  shown 
by  the  dotted  lines,  in  order  that  the  arch  may  be  in  equi- 
librium. 

To  find  what  will  be  the  thrust  at  the  abutments,  or  at 
any  point  in  the  arch,  draw  a  c,  touching  the  curve,  the  ver- 
tical line  ah  any  convenient  length,  and  the  horizontal 
line  h  Cj  then  the  lengths  of  the  lines  a    ah,  and  h  c,  will  be 


46 


RUDIMENTS  OF  THE 


respectively  as  the  thrust  of  the  arch  at  a,  in  the  direction  a  c, 

and  the  vertical  pressure  and  horizontal  thrust  into  which  it 
is  resolved  ;  and  the  weight  of  that  part  of  the  arch  between 
its  centre  and  the  point  a,  which  is  represented  by  a  h,  being 
known,  the  other  forces  are  readily  calculated  from  it. 

69.  When  the  form  of  an  arch  does  not  exactly  coincide^ 
with  its  curve  of  equal  horizontal  thrust,  there  wdll  always 
be  some  minimum  thickness  necessary  to  contain  this  curve, 
and  to  insure  the  stability  of  the  arch.  In  a  semicircular,  fig. 
21,  whose  thickness  is  one-ninth  of  its  radius,  the  line  of  equal 
horizontal  thrust  just  touches  the  extrados  at  the  crown,  and 
the  intrados  at  the  haunches,  pointing  out  the  places  where 
failure  would  take  place  with  a  less  thickness  or  an  unequal 
load,  by  the  voussoirs  turning  on  their  edges.  Those  arches 
which  differ  most  from  their  curves  of  equal  horizontal  thrust 
are  semicircles  and  semi-ellipses,  which  have  a  tendency  to 
descend  at  their  crowns  and  to  rise  at  their  haunches,  unless 

Fig,  21. 


they  are  well  lacked  up.  Pointed  arches  have  a  tendency  to 
rise  at  the  crown  ;  and,  to  prevent  this,  the  cross  springers 
of  the  ribbed  vaults  of  the  middle  ages  were  often  made  of  a 
semicircular  profile,  their  flatness  at  the  crown  being  con- 
cealed by  the  bosses  at  their  intersections. 

70.  If  the  experiment  be  tried  of  equilibrating,  in  the 
manner  above  described,  a  suspended  semicircular  or  semi- 


ART  OF  BUILDING. 


4t 


elliptical  arch,  it  will  be  found  to  be  practically  impossible, 
as  the  weight  required  for  that  purpose  becomes  infinite  at 
the  springing.  This  difficulty  does  not  exist  in  practice,  for 
that  part  of  an  arch  which  lies  beyond  the  plane  of  the  face 
of  the  abutment  in  reality  forms  a  part  of  the  abutment 
itself  (fig.  21 

The  Gothic  architects  well  understood  this,  and  in  their 
vaulted  roofs  built  this  portion  in  horizontal  courses  as  part 
of  the  side  walls  (fig.  22),  commencing  the  real  arch  at  a 
point  considerably  above  the  spinging. 

11.  The  depth  of  the  voussoirs  in  any  arch  must  be  suflfi- 


Fig.  22.^ 


cient  to  contain  the  curve  of 
equilibrium  under  the  greatest 
load  to  which  it  can  be  exposed ; 
and,  as  the  pressure  on  the  arch 
stones  increases  from  the  crown 
to  the  springing,  their  depth 
should  be  increased  in  the  same 
proportion.  Each  joint  of  the 
voussoirs  should  be  at  right 
angles  to  a  tangent  to  the  curve 
of  equilibrium  at  the  point 
throught  which  it  passes. 
72.  Brick  Arches. — In  building  arches  with  bricks  of  the 
common  shape,  which  are  of  the  same  thickness  throughout 
their  length,  a  difficulty  arises  from  the  thickness  of  the  mor- 
tar joints  at  the  extrados  being  greater  than  at  the  intrados, 
thus  causing  settlement  and  sometimes  total  failure.  To 
obviate  this  difficulty,  it  is  usual  to  build  brick  arches  in  se- 
parate rings  of  the  thickness  of  half  a  brick,  having  no  con- 
nection with  each  other  beyond  the  adhesion  of  the  mortar 
or  cement,  except  an  occasional  course  of  headings  where 
the  joints  of  two  rings  happen  to  coincide.    There  is,  how- 


*  This  diagram  is  slightly  altered  from  one  of  the  illustrations  to  Professor 
Willis's  paper  '-On  the  Construction  of  the  Vaults  of  the  Middle  Ages,"  in  th© 
Transactions  of  the  Royal  Institute  of  British  Architects,  Vol.  I.,  Part  2. 


48 


RUDIMENTS  OP  THE 


ever,  a  strong  objection  to  this  plan,  viz.,  that,  if  the  curve 
of  equal  horizontal  thrust  do  not  coincide  with  the  curvature 
of  the  arch,  the  line  of  pressure  will  cross  the  rings,  and 
cause  them  to  separate  from  each  other. 

73.  The  preferable  plan  will  be,  therefore,  to  bond  the 
brick-work  throughout  the  whole  thickness  of  the  arch,  using 
either  cement  or  hard-setting  mortar,  which  will  render  the 
thickness  of  the  joints  of  comparatively  little  importance. 

Cement,  however,  is  not  so  well  suited  for  this  purpose  as 
the  hard  setting  mortars  made  from  the  Lias  limes,  because 
it  sets  before  the  work  can  be  completed  ;  and  in  case  of  any 
settlement,  however  trifling,  taking  place  on  the  striking  of 
the  centres,  the  work  becomes  crippled.  It  is  therefore  pref- 
erable to  use  some  hard  setting  mortar,  which  does  not, 
however,  set  so  quickly  as  cement,  thus  allowing  the  arch  to 
adjust  itself  to  its  load,  or,  in  technical  language,  to  take  its 
hearing,  before  the  mortar  becomes  perfectly  hard. 

72.  We  have  in  the  preceding  remarks  considered  an 
equilibrated  arch  as  a  curved  beam,  every  part  of  which  is 
in  a  state  of  compre^^sion  ;  and,  in  an  arch  composed  of  stone 
voussoirs,  this  is  practically  the  case. 

We  may,  however,  by  the  employment  of  other  materials, 
as  cast  iron  and  timber,  construct  arches  whose  forms  differ 
very  materially  from  their  curves  of  equal  horizontal  thrust. 

Thus  the  semicircular  arch  (^fig.  21,)  which,  if  built  of 
stone  voussoirs  small  in  proportion  to  the  span  of  the  arch, 
would  fail  by  the  opening  of  the  joints  at  a  and  Z>,  might  be 
safely  constructed  with  cast-iron  ribs,  with  the  joints  placed 
at  c  and  d,  the  metal  at  the  points  a  and  b  being  exposed  to 
a  cross-strain  precisely  similar  to  that  of  a  horizontal  beam 
loaded  in  the  centre. 

73.  Laminated  arched  beams,  formed  of  planks  bent 
round  a  mould  to  the  required  curve  and  bolted  together, 
have  been  extensively  used  in  railway  bridges  of  large  span 
during  the  last  ten  years,  and  from  their  comparative  elasti- 
city, and  the  resistance  they  offer  to  both  tension  and  com- 


ART  OF  BUILDING. 


49 


pression,  are  very  well  adapted  to  structures  of  this  kind, 
which  have  to  sustain  very  heavy  loads  passing  with  great 
rapidity  over  them. 

It  is  to  be  regretted,  however,  that  the  perishable  nature 
of  the  material  does  not  warrant  their  long  duration,  not- 
withstanding every  precaution  that  can  be  taken  for  the 
preservation  of  the  timber, 

t4.  SJcew  Arches, — In  ordinary  cases  the  plan  of  an  arch 
is  rectangular,  the  faces  of  the  abutments  being  at  right 
angles  to  the  fronts  ;  but  of  late  years  the  necessity  which 
has  arisen  on  railway  works  of  carrying  communications 
across  each  other  without  regard  to  the  angle  of  their  inter- 
section, has  led  to  the  construction  of  oblique  or  skew 
arches. 

15.  In  an  ordinary  rectangular  arch  each  course  is  parallel 
to  the  abutments,  and  the  inclination  of  any  bed  joint  with 
the  horizon  will  be  the  same  at  every  part  of  it.  In  a  skew 
arch  it  is  not  possible  to  lay  the  courses  parallel  to  the  abut- 
ments, for,  were  this  done,  the  thrust  being  at  right  angles 
to  the  direction  of  the  courses,  a  great  portion  of  the  arch 
on  each  side  would  have  nothing  to  keep  it  from  falling.  In 
order  to  bring  the  thrust  into  the  right  direction,  the  courses 
must  therefore  be  laid  as  nearly  as  possible  at  right  angles 
to  the  fronts  of  the  arch  (see  fig.  23,)  and  at  an  angle  with 


of  each  bed  joint  with  the  horizon  will  increase  from 
the  springing  to  the  crown,  causing  the  beds  to  be  winding 
surfaces  instead  of  a  series  of  planes,  as  in  a  rectangular 
arch.  The  variation  in  the  inclination  of  the  bed  joints 
is  called  the  twist  of  the  beds,  and  leads  to  many  diffi- 
cult problems  in  stone-cutting,  the  consideration  of  which 

4 


Fig,  23. 


the  abutments  ;  and  it  is 
this  which  produces  the  pe- 
culiarity of  the  skew  arch. 
The  two  ends  of  any  course 
will  then  be  at  different 
heights,  and  the  inclination 


50 


KUDIMENTS  OF  THE 


would  be  unsuited  to  the  elementary  character  of  this  little 
work. 

76.  Centering. — The  cemtering  of  an  arch  is  the  temporary 
framework  which  supports  it  during  its  erection,  and  is 
formed  of  a  number  of  ribs  or  centres^  on  which  are  placed  the 
planks  or  laggings  on  which  the  work  is  built. 

77.  In  designing  centres,  there  are  three  essential  points 
to  be  kept  in  view.  1st,  that  there  should  be  sufficient 
strength  to  prevent  any  settlement  or  change  of  form  during 
the  erection  of  the  arch.  2d,  that  means  should  be  pro- 
vided for  easing  or  lowering  the  centre  gradually  from 
under  any  part  of  the  arch.  3d,  that,  as  the  con- 
struction of  centres  generally  involves  the  use  of  a  large 
quantity  of  timber  merely  for  a  temporary  purpose,  all 
unnecessary  injury  to  it  should  be  avoided,  in  order  that 
its  value  for  subsequent  use  may  be  as  little  diminished  as 
possible. 

78.  Where  the  circumstances  of  the  case  do  not  admit  of 
piles  or  other  supports  being  placed  between  the  piers,  it 
becomes  necessary  to  construct  a  trussed  framing  resting  on 
the  piers,  and  of  sufficient  strength  to  support  the  weight  of 
the  arch.  The  tendency  of  this  form  of  centre  to  rise  at  the 
crown,  from  the  great  pressure  thrown  upon  the  haunches 
during  the  erection  of  the  arch,  renders  it  necessary  to 
weight  the  crowns  with  blocks  of  stone  until  it  is  nearly  com- 
pleted. Centres  of  this  kind  are  always  costly,  and  afford 
little  facilities  for  easing. 

79.  Abutments. — The  tendency  of  any  arch  to  overturn  its 
abutments,  or  to  destroy  them  by  causing  the  courses  to 
slide  over  each  other,  may  be  counteracted  in  three  ways. 
1st,  the  arch  may  be  continued  through  the  abutment  until 
it  rests  on  solid  foundation,  as  in  fig.  24.  2d,  by  building 
the  abutments  so  as  to  form  a  horizontal  arch,  the  thrust 


ART  OF  BUILDING. 


51 


Fig.  24. 


being  thrown  on  the  wing  walls,  which  act  as  but- 
tresses (fig.  24.)     3d,  where  neither  of  these  expedients 


Fig.  25. 


is  practicable,  by  joggling  the  courses  together  with 
bed-dowel  joggles,  so  as  to  render  the  whole  abutment 
one  solid  mass. 

80.  Wing  Walls. — Where  the  wing  walls  of  a  bridge  are 
built  as  shown  in  fig.  26,  the  pressure  of  the  earth  will 
always  have  a  tendency  to  fracture  them  at  their  junctioa 


52 


RUDIMENTS  OF  THE 


Fig.  26. 


with  the  abutments,  as  shown  by  the  lines  ah,  c  d.  Equal 
strength  with  the  same  amount  of  material  will  be  obtained 
by  building  a  number  of  thin  longitudinal  and  cross  walls,  as 
shown  in  fig.  2Y,  by  which  means,  the  earth  being  kept  from 

Fig.  27. 


the  back  of  the  walls,  there  is  no  tendency  to  failure  of  this 
kind. 

81.  Vaulting. — The  ordinary  forms  of  vaults  may  be 
classed  under  three  heads,  viz.,  cylindrical,  coved,  and  groined. 

A  cylindrical  vault  is  simply  a  semicircular  arch,  the  ends 
of  which  are  closed  by  upright  walls,  as  shown  in  fig.  28. 


ART  OF  BUILDING. 


53 


When  a  vault  springs  from  all  the  sides  of  its  plan,  as  in  fig. 
29,  it  is  said  to  be  coved.    When  two  cylindrical  vaults  in- 

Fig,  28.  Fig.  29. 


tersect  each  other,  as  in  fig.  30,  the  intersections  of  the 
vaulting  surfaces  are  called  groins j  and  the  vault  is  said  to 
Tbe  groined. 

82.  In  the  Roman  style  of  architecture,  and  in  all  common 
vaulting,  the  vaulted  surfaces  of  the  several  compartments 
are  portions  of  a  continuous  cylindrical  surface,  and  the  pro- 
file of  a  groin  is  simply  an  oblique  section  of  a  semi-cylinder. 

83.  Gothic  ribbed  vaulting  is,  however,  constructed  on  a 
totally  different  principle.  It  consists  of  a  framework  of 
light  stone  ribs  supporting  thin  panels,  whence  this  mode  of 
construction  has  obtained  the  name  of  rih  and  jpannel  vault- 
ing. The  curvature  of  the  diagonal  ribs  or  cross  springers, 
and  of  the  intermediate  ribs,  is  not  governed  in  any  way  by 
the  form  of  the  transverse  section  of  the  vault,  and  in  this 
consists  the  peculiarity  of  ribbed  vaulting.  This  will  be  un- 
derstood by  a  comparison  of  figs.  30  and  31. 


Fig.  30.  Fig.  31. 


Roman  vaulting.  Gothic  vaulting. 


84.  Domes  are  vaults  on  a  circular  plan.  The  equili- 
brium of  a  dome  depends  on  the  same  conditions  as  that  of  a 
common  arch,  but  with  this  difference,  that,  although  a 
dome  may  give  way  by  the  weight  of  the  crown  forcing  out 
the  haunches,  failure  by  the  weight  of  the  haunches  squeez- 


54 


RUDIMENTS  OF  THE 


ing  up  the  crown  is  impossible,  on  account  of  the  support  the 
voussoirs  of  each  course  receive  from  each  other. 

MASONRY  BRICKWORK  BOND. 

85.  The  term  masonry  is  sometimes  applied  generally  to 
all  cemented  constructions,  whether  built  of  brick  or  stone  ; 
but  generally  the  use  of  the  term  is  confined  exclusively  to 
stone-work. 

86.  There  are  many  kinds  of  masonry,  each  of  which  is 
known  by  some  technical  term  expressive  of  the  manner  in 
which  the  stone  is  worked;  but  they  may  all  be  divided  un- 
der three  heads. 

1st.  Rubble  work  (fig.  32,)  in  which  the  stones  are 
used  without  being  squared. 

2nd.  Coursed  work  (fig.  33,)  in  which  the  stones  are 
squared,  more  or  less,  sorted  into  sizes,  and  ranged  in 
courses. 


Fig.  32.  Fig,  33.  Fig.  3*i. 


3d.  Ashlar  work'''  (fig.  34),  in  which  each  stone  is 

squared  and  dressed  to  given  dimensions. 

8t.  Different  kinds  of  masonry  are  often  united.  Thus  a 
wall  may  be  built  with  ashlar  facing  and  rubble  backing  ; 
and  there  are  many  gradations  from  one  class  of  masonry  to 
another,  as  coursed  rubble,  which  is  an  intermediate  step 
between  rubble  work  and  coursed  work. 

88.  In  ashlar  masonry,  the    stability  of  the  work  is 


*  In  London,  the  term  "  ashlar"  is  commonly  applied  to  a  thin  facing  of  stono 
placed  in  front  of  brickwork. 


ART  OF  BUILDING. 


55 


independent,  in  ordinary  eases,  of  the  adhesion  of  the  mortar. 
Kubble  work,  on  the  contrary,  depends  for  support  in  a  great 
measure  upon  it. 

89.  In  dressing  the  beds  of  ashlar  work,  care  must  be 
taken  not  to  work  them  hollow,  so  as  to  throw  the  pressure 
upon  the  edges  of  the  stones,  as  this  leads  to  unsightly 
fractures,  as  b  Z>,  fig.  34. 

90.  Where  there  is  a  tendency  of  the  courses  to  slide  on 
each  other  from  any  lateral  pressure,  it  may  be  prevented  by 
bed-dowel  joggles,  as  shown  at  a  a,  fig  34. 

91.  Where  the  facing  and  the  backing  of  a  wall  do  not 
contain  the  saane  number  of  courses,  as  in  the  case  of  a 
brick  wall  with  stone  facings  (fig.  35)  the  work  will  be 
liable  to  settle  on  the  inside,  as  shown  by  the  dotted  lines, 
from  the  greater  number  of  mortar  joints.  The  only  way 
of  preventing  this  is  to  set  the  backing  in  cement,  or  some 
hard  and  quick-setting  mortar. 

Fig.  35. 

92.  In  facing  brickwork  with  stone  ashlar, 
^  the  stones  should  be  all  truly  squared,  and 
/  worked  to  sizes  that  will  bond  with  the  brick- 
/  work.   If  this  be  neglected,  there  will  be  numer- 
/    ous  vacuities  in  the  thickness  of  the  wall  ( see 

fig.  35),  and  the  facing  and  backing  will  have 
a  tendency  to  separate. 

93.  Bond,  in  masonry,  consists  in  the  placing 
of  the  stones  in  such  relative  positions  that  no 

joint  in  any  course  shall  be  in  the  same  plane  with  any  other 
joint  in  the  course  immediately  above  or  below  it.  This  is 
called  breaking  joint. 

94.  Stones  placed  lengthwise  in  any  work  are  called 
stretchersj  and  those  placed  in  a  contrary  direction  are 


RUDIMENTS  OF  THE 


called  headers.    When  a  header  extends 
36.         throughout  the  whole  thickness  of  a  wall. 


rzi 


J  I ,  i  i  i  T  □zr 


x5 


it  is  called  a  through, 

95.  There  are  two  kinds  of  bond  made 
use  of  by  bricklayers,  called  respectively 
English  bond  and  Flemish  bond.  In  the 
EagiiBh  Bond.  g^^^  couTScs  are  laid  alternately  with 
headers  and  stretchers  (fig,  36J  ;  in  the 
second,  the  headers  and  stretchers  alter- 


i  I  1  1  i  1  I  ill 


I'.i  1,  ,11,  jh 


^^^^ 


i!»  >!  !i  !iT 


nate  in  the  same  course  ("fig.  This 
is  considered  to  have  the  neatest  appear- 
ance :  butj,  as  the  number  of  headers  re- 
Fiemiiiii  Bond.  qnircd  is  fewer  than  in  English  bond, 
there  is  not  so  much  lateral  tie,  and  on 
this  account  it  is  considered  to  be  much  inferior  to  it  in 
strength.  A  common  practice,  which  cannot  be  too  much 
reprobated,  is  that  of  building  brick  walls  with  two  qualities 
of  bricks,  without  any  bond  between  them,  the  headers  of 
the  facing  bricks  being  cut  in  two  to  save  the  better  material, 
thus  leaving  an  upright  joint  between  the  facing  and  back- 
ing. 

95.  In  building  upright  walls,  which  have  to  sustain  a 
Yertical  pressure^  three  leading  principles  must  be  kept  in 
view. 

1.  Uniformity  of  construction  throughout  the  whole 
thickness. 

2.  The  bonding  of  the  work  together. 
8.  The  proper  distribution  ef  the  load. 

96.  Uniformity  of  Con^ruetio%. — We  have  already  spoken 
of  the  danger  arising  from  the  backing  of  a  wall  containing 
more  compressible  material  than  the  facing  ;  but  it  cannot 
be  too  often  repeated,  that  in  all  building  operations  it  is  not 
the  amotmt^  but  irregularity  of  settlement  which  is  so  danger- 
ous. Thus  a  rubble  wall,  with  proper  care,  may  be  carried 
up  to  a  great  height,,  and  bear  safely  the  weight  of  the  floors 
and  roof  of  a  large  building,  whilst  a  wall  built  of  bricks 


ART  OF  BUILDING. 


5t 


and  mortar,  and  faced  with  dressed  ashlar,  will,  under  similar 
circumstances,  be  fractured  from  top  to  bottom,  from  the 
difference  in  settlement  of  the  facing  and  backing. 

It  is  a  common  but  vicious  practice  to  build  the  ends  of 
joists  and  other  timbers  into  the  walls,  and  to  rest  the 
superincumbent  work  upon  them.  This  is  liable  to  lead  to 
settlements  from  the  shrinking  of  the  timber,  and  should 
always  be  guarded  against  by  leaving  proper  recesses  for  the 
ends  of  the  timbers,  so  that  the  strength  of  the  masonry  or 
brick-work  shall  be  quite  independent  of  any  support  from 
them. 

91.  Bond, — In  addition  to  the  bonding  together  of  the 
materials  above  described,  a  further  security  against  irregular 
settlement  is  usually  provided  for  brick  walls,  in  the  shape 
of  ties  of  timber,  called  hoTid^  which  are  cut  of  the  depth 
and  thickness  of  a  brick,  and  built  into  the  work. 
There  is,  however,  a  great  objection  to  the  use  of  timber 
in  the  construction  of  a  wall,  as  it  shrinks  away  from 
the  rest  of  the  work,  and  often  endangers  its  stability  by 
rotting. 

98.  Instead  of  bond  timbers,  hoop-iron  bond  is  now 
very  generally  used.  This  is  formed  of  iron  hooping, 
tarred,  to  protect  the  iron  from  contact  with  the 
mortar,  and  laid  in  the  thickness  of  the  mortar  joints. 
This  forms  a  very  perfect  longitudinal  tie,  and  has  all 
the  advantages,  with  none  of  the  disadvantages,  of  bond 
timbers. 

99.  Distribution  of  the  Load, — It  is  always  advisable, 
when  a  heavy  load  has  to  be  supported  on  a  few  points,  as 
in  the  case  of  a  larger  floor  resting  on  girders,  to  bring  the 
weight  as  nearly  as  possible  on  the  centre  of  the  wall,  and 
to  distribute  it  over  a  large  bearing  surface,  by  stone  bond- 
ing through  its  whole  thickness  j  this  arrangement  is  shown 
in  figures  38  and  39. 


58 


RUDIMENTS  OF  THE 


Fig,  38.  Fig.  39. 


100.  It  is  of  importance  in  designing  buildings  to  arrange 
the  apertures  for  doors,  windows,  &e.,  in  tlie  different  floors, 
so  that  openings  shall  be  over  openings,  and  piers  over  piers  ; 
if  this  be  not  attended  to,  it  is  scarcely  possible  to  prevent 
settlements.  In  addition  to  this,  as  the  pressure  on  the 
foundations  will  be  greatest  under  the  piers,  it  is  desirable  to 
connect  these  with  inverted  arches,  by  which  means  the 
weight  is  distributed  equally  over  the  whole  surface  of  the 
foundations. 

101.  All  openings  in  walls  for  doors,  windows,  gate-ways, 
&c.,  should  be  arched  over  throughout  the  whole  thickness 
of  the  walls  in  which  they  occur  ;  and  wooden  lintels  and 
bressummers  should  only  be  introduced  as  ties  to  counteract 
the  thrust  of  the  arches,  and  as  attachments  for  the  internal 
finishings. 

102.  Bressummers  of  cast  iron  are  often  used  for  support- 
ing the  walls  of  houses  over  large  openings,  as  in  the  case 
of  shop  fronts  ;  but  they  have  the  disadvantage  of  being 
liable  to  be  cracked,  in  case  of  fire,  if  water  is  thrown  on 
them  whilst  in  a  heated  state,  which  renders  their  use  very 
objectionable,  as  no  dependence  can  be  placed  upon  them 
after  having  been  suddenly  cooled  in  this  manner,  even  if 
they  do  not  actually  break  at  the  time. 

PARTITIONS. 

103.  The  partitions  forming  the  interior  divisions  of  a  ' 
building  may  be  either  solid  walling  of  brick  or  stone,  or 


ART  OF  BUILDING. 


59 


ttey  may  be  constructed  entirely  of  timber,  or  they  may  be 
frames  of  timber  filled  in  with  masonry  or  brick-work. 

It  will  always  be  best,  both  for  durability  and  security 
against  fire,  to  make  the  partitions  of  solid  w^alling  ;  bat 
this  is  not  always  practicable,  and,  in  the  erection  of  dwelling 
houses,  they  are  for  the  most  part  made  of  timber. 

The  principles  to  be  kept  in  view  in  the  construction  of 
framed  timber  partitions  are  very  simple.  Care  must  be 
taken  to  avoid  any  settlement  from  cross  strain,  and  they 
should  not  in  any  way  depend  for  support  upon  subordinate 
parts  of  the  construction,  but  should  form  a  portion  of  the  main 


Fig,  40. 


carcase  of  the  building,  and  be  quite  independent  of  the  floors, 
which  should  not  support,  but  should  be  supported  by  them. 


60 


RUDIMENTS  OF  THE 


Where  a  partition  extends  througli  two  or  more  stories  of 
a  building,  it  should  be  as  much  as  possible  a  continuous 
piece  of  franiing,  with  strong  sills  at  proper  heights  to  sup- 
port the  floor  joists. 

Where  openings  occur,  as  for  folding  doors,  or  where  a 
partition  rests  on  the  ends  of  the  sill  only,  it  should  be 
strongly  trussed,  so  that  it  is  as  incapable  of  settlement  as 
the  walls  themselves.  From  want  of  attention  to  these 
points,  we  frequently  see  in  dwelling-houses  floors  which  have 
sunk  into  curved  lines,  doors  out  of  square,  cracked  ceilings 
and  broken  cornices,  and  gutters  that  only  serve  to  conduct 
the  roof  water  to  the  interior  of  the  building,  to  the  injury 
of  ceilings  and  walls,  and  the  great  discomfort  of  its  inmates. 
The  above  remarks  will  be  better  understood  by  a  study  of 
fig.  40,  which  is  an  example  of  a  framed  partition  extending 
through  three  stories  of  a  dwelling  house. 

FLOORS. 

104.  The  assemblage  of  timbers  forming  any  naked  floor- 
ing may  be  either  single  or  double.  Single  flooring  is  formed 
with  joists  reaching  from  wall  to  wall,  where  they  rest  on 
;plates  of  timber  built  into  the  brick-work,  as  in  fig.  41.  The 
floor  boards  are  nailed  over  the  upper  edges  of  the  joists. 


Fig.  41. 


Single  flooring. 


whose  lower  edges  receive  the  lathing  and  plastering  of  the 
ceilings.  Double  floors  are  constructed  with  stout  Unding 
joists  J  a  few  feet  apart,  reaching  from  wall  to  wall,  and  sup 


ART  OF  BUILDING. 


61 


porting  ceiling  joists  which  carry  the  ceiling  ;  and  bridging 
joists^  on  which  are  nailed  the  floor  boards  ("fig.  42.) 

Fig,  42. 


Double  flooring. 


In  douUe-frar:  d  floorings  the  binders,  instead  of  resting 
in  the  walls,  ar  j  supported  on  girders^  as  shown  in  fig.  43. 
Single  flooring  is,  in  many  respects,  inferior  to  double  floor- 


Fig.  43. 


Double-framed  flooring. 


ing,  being  liable  to  sag^  or  deflect,  so  as  to  make  the  floor 
concave  ;  and  the  vibration  of  the  joists  occasions  injury  to 
the  ceilings,  and  also  shakes  the  walls.  In  double  flooring 
the  stiffness  of  the  binders  and  girders  prevents  both  deflection 
and  vibration,  and  the  floors  and  ceilings  hold  their  lines ^  that  is, 
retain  their  intended  form  much  better  than  in  single  flooring. 


62 


RUDIMENTS  OF  THE ' 


105.  The  joists  in  a  single  floor  are  usually  laid  on  a  plate 
built  into  the  wall,  as  shown  in  fig.  41  ;  it  is,  however,  pre- 
ferable to  rest  the  plate  on  projecting  corbels,  which  prevents 
the  wall  being  crippled  in  any  way,  by  the  insertion  of  the 
joists.  The  plates  of  basement  floors  are  best  supported  on 
small  piers  carried  up  from  the  footings.  This  is  an  impor- 
tant point  to  be  attended  to,  as  the  mo. -^duction  of  timber 
into  a  wall  is  nowhere  likely  to  be  productive  of  such  in- 
jurious eflects  as  at  the  foundations,  where,  from  damp  and 
imperfect  ventilation,  all  wood-work  is  liable  to  speedy 
decay. 

The  ends  of  all  girders  should  rest  in  recesses,  formed  as 
shown  in  figs.  38  and  39,  and  with  a  space  for  the  free  cir- 
culation of  air  round  the  timber,  which  is  one  of  the  best 
preventives  of  decay. 

The  manner  in  which  ceiling  joists  ant  bridging  joists 
are  framed  to  the  binders,  and  these  latter  tenoned  into  the 
girders,  is  shown  in  figs.  44,  45,  46,  and  4.1. 


Fig.  44. 


Fig.  45. 


Fig.  46. 


BRIDCINC  JOIST 


BRIDCINC  .JOIST 


Fig.  47. 


FLOOR  BOABD^-_ 


PJLASTERINa 

a  a,  bridging  joists  ;  b  b,  ceiling:  joists  ;  c,  girder 

106.  Fire-proof  floors  are  usually  constructed  with  iron 
girders  a  short  distance  apart,  which  serve  as  abutments  for 
a  series  of  brick  arches,  on  which  either  a  wooden  or  plaster 
floor  may  be  laid  (see  fig.  48). 


ART  OF  BUILDING. 
Fig,  48. 


6S 


w 

107.  Of  late  years  many  terraces  and  flat  roofs  have  been 
constructed  with  two  or  more  courses  of  plain  tiles,  set  in 
cement,  and  breaking  joint  with  each  other,  supported  at 
short  intervals  by  cast-iron  bearers,  as  shown  in  fig.  49. 


Fig,  49. 


This  mode  of  construction,  although  appearing  very  slight, 
possesses  great  strength,  and  is  now  very  much  used  in  and 
about  London,  and  in  some  portions  of  the  United  States. 


ROOFING. 

108.  In  roofs  of  the  ordinary  construction,  the  roof  cover- 
ing is  laid  upon  rafters  supported  by  horizontal  pirlins,  which 
rest  on  upright  trusses  or  frames  of  timber,  placed  on  the 
walls  at  regular  distances  from  each  other.  Upon  the 
framing  of  the  trusses  depends  the  stability  of  the  roof,  the 
arrangement  of  the  rafters  and  purlins  being  subordinate 
matters  of  detail.  The  timbering  of  a  roof  may  be  compared 
to  that  of  a  double-framed  floor,  the  trusses  of  the  former 
corresponding  to  the  girders  of  the  latter,  the  purlins  to  the 
binders,  and  the  rafters  to  the  joists. 

Timber  roofs  may  be  divided  under  two  heads — 

1st.  Those  which  exert  merely  a  vertical  pressure  on  the 
walls  on  which  they  rest. 

2d.  Those  in  which  advantage  is  taken  of  the  strength  of 
the  walls  to  resist  a  side  thrust,  as  in  many  of  the  Gothic 
open  timbered  roofs. 


64 


RUDIMENTS  OF  THE 


109.  Trussed  Roofs ^  exerting  no  Side  Thrust  on  the  Walls, 
— In  roofs  of  this  kind  each  truss  consists  essentially  of  a  pair 
of  principal  rafters  or  principals^  and  a  horizontal  tie  hcam^ 
and  in  large  roofs  these  are  connected  and  strengthened  by 
king  and  queen  posts  and  struts  (see  figs.  51.  and  52). 

Fig.  50  shows  a  very  simple  truss  in  which  the  tie  is  above 
the  bottom  of  the  feet  of  the  principals,  which  is  often  done 


in  small  roofs  for  the  sake  of  obtaining  height.  The  tie  in 
this  case  is  called  a  collar.  The  feet  of  both  common  and 
principal  rafters  rest  on  a  wall  plate.  The  purlins  rest  on 
the  collar,  and  the  common  rafters  but  against  a  ridge  run- 
ning along  the  top  of  the  roof.  This  kind  of  truss  is  only 
suited  to  very  small  spans,  as  there  is  a  cross  strain  on  that 
part  of  the  principals  below  the  collar,  which  is  rendered 
harmless  in  a  small  span  by  the  extra  strength  of  the  princi- 
pals, but  which  in  a  large  one  would  be  very  likely  to  thrust 
out  the  walls. 

110.  In  roofs  of  larger  span  the  tie  beam  is  placed  below 
the  feet  of  the  principals,  which  are  tenoned  into,  and  bolted 
to  it.  To  keep  the  beam  from  sagging ,  or  bending  by  its 
own  weight,  it  is  suspended  from  the  head  of  the  principals 
by  a  king  post  of  wood  or  iron.  The  lower  part  of  the  king 
post  affords  abutments  for  struts  supporting  the  principals 
immediately  under  the  purlins,  so  that  no  cross  strain  is  ex- 
erted on  any  of  the  timbers  in  the  truss,  but  they  all  act  in 
the  direction  of  their  length,  the  principals  and  struts  being 
subjected  to  compression,  and  the  king  post  and  tie  beam  to 
tension.    Fig.  51  shows  a  sketch  of  a  king  truss.    The  com- 


Fig.  50. 


ART  OF  BUILDING. 


65 


Fig.  51. 


mon  rafters  but  on  a  ;polc  jplate^  the  tie  beams  resting  either 
on  a  continuous  plate,  or  on  short  templates  of  wood  or 
stone. 

111.  Where  the  span  is  considerable,  the  tie  beam  is  sup- 
ported at  additional  points  by  suspension  pieces  called  queen 
posts  (fig.  52),  from  the  bottom  of  which  spring  additional 


Fig.  52. 


struts  ;  and,  by  extending  this  principle  ad  infinitum,  we 
might  construct  a  roof  of  any  span,  were  it  not  that  a  prac- 
tical limit  is  imposed  by  the  nature  of  the  materials.  Some- 
times roofs  are  constructed  without  king  posts,  the  queen 
posts  being  kept  apart  by  a  straining  piece.  This  construc- 
tion is  shown  in  fig.  53,  which  shows  the  design  of  the  old 

5 


66 


RUDIMENTS  OF  THE 


Fig.  63. 


roof  (now  destroyed)  of  the  cliurch  of  St.  Paul,  outside  the 
walls,  at  Rome.  This  truss  is  interesting  from  its  early  date, 
having  been  erected  about  400  years  ago  ;  the  trusses  are  in 
pairs,  a  king  post  being  keyed  in  between  each  pair  to  sup- 
port the  tie  beams  in  the  centre. 

112.  Of  late  years  iron  has  been  much  used  as  a  material 
for  the  trusses  of  roofs,  the  tie  beams  and  suspending  pieces 
being  formed  of  light  rods,  and  the  principals  and  struts  of  , 
rolled  T  or  angle  iron,  to  which  sockets  are  riveted  to  receive 
the  purlins. 


Fig,  54. 


113.  The  largest  roof  ever  executed  in  one  span  is  that 
of  the  Imperial  Kiding  House  at  Moscow,  built  in  1790,  of 
which  the  span  is  235  ft.  (fig.  54).    The  principal  feature  in 


ART  OF  BUILDING, 


6t 


this  roof  is  an  arched  beam,  the  ends  of  which  are  kept  from 
spreading  by  a  tie  beam,  the  two  being  firmly  connected  by 
suspension  pieces  and  diagonal  braces  :  the  arched  beam 
(fig.  55).  is  formed  of  three  thicknesses  of  timber,  notched 

Fig,  55. 


out  to  prevent  their  sliding  on  each  other, — a  method  which 
is  objectionable  on  account  of  the  danger  of  the  splitting  of 
the  timber  under  a  considerable  strain, 
j  114.  The  principle  of  the  bow  suspension  truss,  as  this  sys- 
tem of  trussing  is  called,  has  been  much  used  within  the  last 
ten  years  for  railway  bridges  and  similar  works.  One  of  the 
best  executed  works  of  this  kind  is  a  bridge  over  the  River 
Ouse,  near  Downham  Market,  in  Norfolk,  on  the  line  of  the 
Lynn  and  Ely  Railway,  the  trusses  of  which  are  150  ft. 
span. 

115.  Roofs  on  the  principle  of  the  Arch. — In  the  16th  cen- 
tury, Philibert  de  Lorme,  a  celebrated  French  architect, 
published  a  work,  in  which  he  proposed  to  construct  roofs 
and  domes  with  a  series  of  arched  timber  ribs  in  place  of 
trusses,  these  ribs  being  formed  of  planks  in  short  lengths, 
placed  edgewise,  and  bolted  together  in  thicknesses,  breaking 
joint  Cfig.  56).  This  mode  of  construction  has  been  more 
or  less  used  ever  since  the  time  of  its  author.  An  instance 
of  its  successful  application  on  a  large  scale  was  the  original 
dome  of  the  Halle  au  Ble,  at  Paris,  120  ft.  in  diameter,  built 
by  Messrs.  Legrand  and  Molino.    This  roof  has  since  been 


Fig,  56. 


replaced  by  an  iron  one,  the  original  dome  having  been  de- 
stroyed by  fire. 


68 


RUDIMENTS  OF  THE 


116.  There  are,  however,  some  great  disadvantages,  con- 
nected with  this  system.  There  is  considerable  waste  of 
material  ;  the  labor  is  great  as  compared  with  roofs  of  simi- 
lar span  of  the  ordinary  construction  ;  and,  as  the  chief 
strength  of  the  rib  depends  upon  the  lateral  cohesion  of  the 
fibres  of  the  wood,  it  is  necessary  to  provide  such  an  amount 
of  surplus  strength  as  shall  insure  it  against  the  greatest 
cross  strain  to  which  it  can  be  exposed  from  violent  winds 
or  otherwise. 

11k  Struck  by  these  disadvantages.  Colonel  Emy,  a 
French  military  engineer,  proposed,  in  ISIT,  an  improve- 
ment on  the  system  of  Philibert  de  Lorme,  which  was  pre- 
cisely the  laminated  arched  rib  so  much  in  use  at  the  present 
day.  It  was  not  until  1825  that  he  obtained  permission  to 
put  his  design  into  execution  in  the  erection  of  a  large  roof 
65  ft.  span  at  Marac,  near  Bayonne  (fig.  b1).    The  ribs  in 


Fig.  57. 


ART  OF  BUILDING. 


69 


this  roof  are  formed  of  planks  bent  round  on  templets  to  the 
proper  curve,  and  kept  from  separating  by  iron  straps,  and 
also  by  the  radiating  struts  which  are  in  pairs,  notched  out 
so  as  to  clip  the  rib  between  them. 

The  principle  of  the  roof  is  exceedingly  good.  The  prin- 
cipals, wall-posts,  and  arched  rib,  form  two  triangles,  firmly 
braced  together,  and  exerting  no  thrnst  on  the  walls  ;  and  * 
the  weight  of  the  whole  roof  being  thrown  on  the  walls  at 
the  feet  of  the  ribs,  and  not  at  the  pole  plate,  the  walls  are 
not  tried  by  the  action  of  a  heavy  roof,  and  the  consequent 
saving  in  masonry  is  very  great. 

The  great  difference  in  principle  between  the  arched  rib 
of  Philibert  de  Lorme,  and  the  laminated  rib  of  Colonel  Emy 
is,  that  in  the  latter  the  direction  of  the  fibre  of  the  wood 
coincides  with  the  curvature  of  the  rib  ;  and,  as  a  conse- 
quence of  this,  the  joints  are  much  fewer  ;  the  rib  possesses 
considerable  elasticity,  so  as  slightly  to  yield  rather  than 
break  under  any  violent  strain  ;  and,  from  the  manner  in 
which  the  planks  are  bolted  together,  it  is  impossible  for  the 
rib  to  give  way,  unless  the  force  applied  be  sufficient  to  crush 
the  fibres. 

The  principle  of  the  laminated  arched  rib  has  been  exten- 
sively used  in  the  erection  of  railway  bridges  in  England. 

118.  Gothic  Roofs, — The  open  timber  roofs  of  the  middle 
ages  come,  for  the  most  part,  under  the  second  class,  viz., 
those  which  exert  more  or  less  thrust  upon  the  walls,  al- 
though there  are  many  fine  examples  in  which  this  is  not  the 
case. 

We  propose  to  describe  the  principal  varieties  of  these 
roofs,  without  reference  either  to  their  decorative  details,  or 
to  their  chronological  arrangement,  our  object  here  being 
simply  to  explain  the  principles  on  which  they  were  con- 
structed. 

119.  Fig.  58,  which  is  a  section  of  the  parish  church  of 
Chaldon,  near  Merstham  in  Surrey,  shows  a  system  of  roof- 
ing formerly  very  common.    This  may  be  compared  to  single 


TO  RUDIMENTS  OF  THE 

Fig.  58. 


flooring,  as  there  are  no  principals,  purlins,  or  even  ridge. 
It  is  a  defective  form  of  roof,  as  the  rafters  have  a  tendency 
to  spread  and  thrust  out  the  walls.  In  the 
n  example  before  us,  this  effect  has  been  pre- 
vented by  the  insertion  of  tie-beams,  from 
LMii  which  the  collars  have  been  propped  up  (fig. 
69),  thus,  in  fact,  balancing  the  roof  on  the 
centres  of  the  collars,  which  are  in  conse- 
quence violently  strained. 

120.  After  the  introduction  of  the  four- 
centered  arch,  a  great  many  church  roofs  of 
the  construction  just  described  were  altered,  as  shown  by 
the  dotted  lines  in  fig.  60,  in  order  to  obtain  more  light  by 


a  post ;  6  sill ; 
o  c  struts. 


Fig.  60. 


the  introduction  of  clerestory 
windows  over  the  nave  arches. 
The  flat  roofs,  which  superseded 
the  former  ones,  were  often 
formed  without  any  truss  what- 
ever, being  simply  an  arrange- 
ment of  main  beams,  purlins, 
and  rafters,  precisely  similar  to 
a  double-framed  floor,  with  the 


ART  OF  BUILDING. 


11 


Fig,  61, 


difference  only  that  the  main  beams,  instead  of  being  per- 
fectly straight,  were  usually  cut  out  of  crooked  timber  so  as 
to  divide  the  roof  into  two  inclined  planes. 

To  throw  the  weight  of  the  roof  as  low  down  as  possible, 
the  ends  of  the  main  beams  are  often  supported  on  upright 
posts  placed  against  the  walls  and  resting 
on  projecting  corbels,  the  wall  posts  and 
beams  being  connected  by  struts  in  such 
a  way  that  deflection  in  the  centre  of  the 
beam  cannot  take  place,  unless  the  load 
be  sufficient  to  force  out  the  walls,  as 
shown  by  the  dotted  lines  in  fig.  61 
The  struts  are  often  cut  out  of  stout  plank,  forming  soHd 
spandrils,  the  edges  of  which  are  moulded  to  suit  the  profile 
of  the  main  beam  (see  fig.  62 J,  which  also  shows  the  man- 


Fig.  62. 


ner  of  securing  the  struts  to  the  wall  posts  and  to  the  beam 
with  tongues  and  wooden  pins. 

121.  Fig.  63  exhibits  a  construction  often  to  be  met  with, 
which,  in  general  appearance,  resembles  a  trussed  king  post 
roof,  but  which  is  in  reality  very  dififerent,  the  tie  beam 
being  a  strong  girder  supporting  the  king  post,  which,  in- 


12 


RUDIMENTS  OF  THE 


stead  of  serving  to  suspend  the  tie-beam  from  the  principals, 
is  a  prop  to  the  latter.  In  this  and  the 
Fig,  63.  previous  example,  any  tending  to  deflection 
of  the  tie-beam  is  prevented  by  struts  :  the 
weight  of  the  roof  is  thrown  by  means  of 
wall  posts  considerably  below  the  feet  of 
the  rafters,  so  that  the  weight  of  the  upper 
part  of  the  wall  is  made  available  to  resist 
the  thrust  of  the  struts. 

122.  The  roofs  we  have  been  describing  are  not  to  be  re- 
commended as  displaying  any  great  amount  of  constructive 
skill.  Indeed,  although  they  answer  very  well  for  small 
spans  with  timbers  of  large  scantling  and  side  walls  of  suffi- 
cient thickness  to  resist  a  considerable  thrust,  they  are 
totally  unsuited  to  large  spans,  and  are  in  every  way  inferior 
to  trussed  roofs. 

The  above  remarks  do  not  apply  to  the  high  pitched  roofs 
of  the  large  halls  of  the  fifteenth  and  sixteenth  centuries, 
which,  for  the  most  part,  are  trussed  in  a  very  perfect  man- 
ner, so  as  to  exert  no  thrust  upon  the  walls  ;  although,  in 
some  instances,  as  at  Westminster  Hall,  they  depend  upon 
the  latter  for  support. 

The  general  design  of  these  roofs  is  shown  in  figs.  64  and 


Fig  64. 


ART  OF  BUILDING. 


t3 


65.  The  essential  parts  of  each  truss  are,  a  pair  of  princi- 
pals connected  by  a  collar  or  wind  learn,  and  two  hamrmr 
beams^  with  queen  posts  over  them,  the  whole  forming  three 
triangles,  which,  if  not  secured  in  their  relative  positions, 
otherwise  than  by  the  mere  transverse  strength  of  the  prin- 
cipals, would  turn  on  the  points  c  c  (fig.  65 J,  the  weight  of 
the  roof  thrusting  out  the  walls  in  the  manner  shown  in  the 
figure.    There  are  two  ways  in  which  a  truss  of  this  kind 


may  be  prevented  from  spreading.  1st,  The  ends  of  the 
hammer  beams  may  be  connected  with  the  collar  by  tension 
pieces,  a  a  (fig.  64),  by  which  the  thrust  on  the  walls  will 
be  converted  into  a  vertical  pressure.  2d,  The  hammer 
beams  may  be  kept  in  their  places  by  struts,  b  b,  the  walls 
being  made  sufficiently  strong  by  buttresses,  or  otherwise,  to 
resist  the  thrust. 

In  existing  examples,  we  find  sometimes  one  and  some- 
times the  other  of  these  plans  followed  ;  and  occasionally 
both  methods  are  combined  in  such  a  manner  that  it  is  often 
difficult  to  say  what  parts  are  in  a  state  of  compression,  and 
what  are  in  a  state  of  tension. 


Fig,  65. 


123.  The  roof  of  the  great  hall  at  Hampton  Court 
(fig.  66)  is  very  strong,  and  so  securely  tied,  that  were  the 


74 


RUDIMENTS  OF  THE 


bottom  struts,  h  removed, 
there  would  be  little  danger  of 
the  principals  thrusting  out 
the  walls  ;  and,  on  the  other 
hand,  from  the  weight  of  the 
roof  being  carried  down  to  a 
considerable  distance  below 
the  hammer  beams  by  the  wall 
posts,  the  walls  themselves  of- 
fer so  much  resistance  to  side 
thrust,  that  there  would  be  no 
injurious  strain  on  them  were 
the  tension  pieces^  a  a,  re- 
moved. 

124.  The  construction  of  the 
roof  of  the  hall  at  Eltham 
Palace,  Kent  (fig.  6t),  differs  very  considerably  from  that 

Fig,  67. 


of  the  Hampton  Court  roof.  The  whole  weight  is  thrown 
on  the  top  of  the  wall,  and  the  bottom  pieces,  h  Z>,  are  merely 
ornamental,  the  tension  pieces,  a     forming  a  complete  tie. 


ART  OF  BUILDING. 


75 


This  has  been  shown  by  a  partial  failure  which  has  taken 
place.  The  wall  plates  having  become  rotten  in  consequence 
of  the  gutters  being  stripped  of  their  lead,  the  weight  has 
been  thrown  on  the  pseudo  struts,  which  have  bent  under 
the  pressure,  and  forced  out  the  upper  portion  of  the  walls. 

125.  The  roof  of  Westminster  Hall  (fig.  68)  is  one  of  the 
finest  examples  now  existing  of  open  timbered  roofs.  The 

Fig.  68. 


peculiar  feature  of  this  roof  is  an  arched  rib  in  three  thick- 


^6 


RUDIMENTS  OF  THE 


nesses,  something  on  the  principle  of  PhiHbert  de  Lorme  ; 
but  it  is  so  shght,  compared  with  the  great  span,  that  it  is 
probable,  in  designing  the  roof,  the  architect  took  full  ad- 
vantage of  the  support  afforded  by  the  thickness  of  the 
walls  and  the  buttresses  ;  if,  indeed,  the  latter  were  not 
added  at  the  time  the  present  roof  was  erected,  in  1395.  It 
has  been  ascertained  that  the  weight  of  the  roof  rests  on  the 
top  of  the  walls,  the  lower  part  of  the  arched  rib  only  serv- 
ing to  distribute  the  thrust,  and  to  assist  in  preventing  the 
hammer  beams  from  sliding  on  the  walls. 

126.  The  mediaeval  architects  generally  employed  oak  in 
the  construction  of  their  large  roofs,  the  timbers  being  mor- 
ticed and  pinned  together,  as  shown  in  fig.  62.  This  system 
of  construction  is  impossible  in  fir  and  other  soft  woods,  in 
which  the  fibres  have  little  lateral  cohesion,  as  the  timber 
would  split  with  the  strain  ;  and  therefore,  in  modern  prac- 
tice, it  is  usual  to  secure  the  connections  with  iron  straps  or 
bolts  passing  round  or  through  the  whole  thickness  of  the 
timbers. 

ROOF  COVERINGS. 

121.  The  different  varieties  of  roof  coverings  principally 
used  may  be  classed  under  three  heads  :  stone,  wood,  and 
metal. 

Of  the  first  class,  the  best  kind  is  slate,  which  is  used 
either  sawn  into  slabs  or  split  into  thin  laminae.  The  differ- 
ent sizes  of  roofing  slate  in  common  use  are  given  in  the 
description  of  Slaters^  Work. 

In  many  parts  of  England,  thin  slabs  of  stone  are  used  in 
the  same  way  as  roofing  slate.  In  the  Weald  of  Sussex  the 
stone  found  in  the  locality  is  much  used  for  this  purpose,  but 
it  makes  a  heavy  covering,  and  requires  strong  timbers  to 
support  it. 

128.  Tiles  are  of  two  kinds  :  jtlain  tiles ^  which  are  quite 
flat ;  and  pantiles ^  which  are  of  a  curved  shape,  and  lap  over 


ART  OF  BUILDING. 


each  other  at  the  sides.  Each  tile  has  a  projecting  ear  on 
its  upper  edge,  by  which  it  is  kept  in  its  place.  Sometimes 
plain  tiles  are  pierced  with  two  holes,  through  which  oak 
pins  are  thrust  for  the  same  purpose. 

129.  Wooden  coverings  are  little  used  at  the  present  day, 
except  for  temporary  purposes  ;  shingles  of  split  oak  were 
formerly  much  used,  and  may  still  be  seen  on  the  roofs  of 
some  country  churches.    Cedar  shingles  are  much  used. 

130.  Metallic  Coverings. — The  metals  used  for  roof  cover- 
ings are  lead,  zinc^  copper,  and  iron. 

131.  Lead  is  one  of  the  most  valuable  materials  for  this 
purpose  on  account  of  its  malleability  and  durability,  the 
action  of  the  atmosphere  having  no  injurious  effect  upon  it. 
Lead  is  used  for  covering  roofs  in  sheets  weighing  from  4  to 
8  lbs.  per  sup.  foot. 

132.  Copper  is  used  for  covering  roofs  in  thin  sheets 
weighing  about  16  oz.  per  sup.  foot,  and  from  its  lightness 
and  hardness  has  some  advantages  over  lead  ;  but  the  ex- 
pense of  the  metal  effectually  precludes  its  general  adoption. 

133.  Zinc  has  of  late  years  superseded  both  lead  and 
copper  to  a  considerable  extent  as  roof  coverings.  It  is  used 
in  sheets  weighing  from  12  oz.  to  20  oz.  per  sup.  foot.  It  is 
considered  an  inferior  material  to  those  just  named  ;  but  its 
lightness  and  cheapness  are  great  recommendations,  and  the 
manufacture  has  been  much  improved  since  its  first  introduc- 
tion. 

134.  Cast  iron,  coated  with  zinc  to  preserve  it  from  rust- 
ing, is  now  much  used  in  a  variety  of  forms.  We  have  already 
mentioned  its  adoption  for  covering  the  roofs  of  the  Kew 
Houses  of  Parliament. 

135.  All  metallic  coverings  are  subject  to  contraction  and 
expansion  with  the  changes  of  the  temperature,  and  great 


RUDIMENTS  OF  THE 


care  is  requisite  in  joining  the  sheets  to  make  them  lap  ^^Jilf 
each  other,  so  as  to  make  the  joints  water-tight,  withoat 
preventing  the  play  of  the  metal. 

The  following  table  of  the  comparative  weights  of  different 
roof  coverings  may  be  useful 

Cwts.  qrs.  lbs. 

Plain  tiles,  per  square  of  100  ft.  sup.  .  18  0  0 
Pantiles  920 

Slating,  an  average   10  0 

Lead,  1  lb.  to  the  sup.  foot  ....  620 
Copper  or  zinc,  16  oz.  do   10  0 


SUPPLY  OF  WATER. 

136.  The  arrangements  fot  distributing  a  supply  of  water 
over  the  different  parts  of  a  building  will  depend  very 
materially  ou  the  nature  of  the  supply,  whether  constant  or 
intermittent. 

The  most  common  method  of  supply  from  water-works  is 
by  pipes  which  communicate  with  private  cisterns,  into  which 
the  water  is  turned  at  stated  intervals. 

A  cistern,  in  a  dwelling-house,  is  always  more  or  less  an 
evil ;  it  takes  up  a  great  deal  of  space,  costs  a  great  deal  of 
money  in  the  first  instance,  and  often  causes  inconvenience, 
from  leakage,  from  the  bursting  of  the  service  pipes  in  frosty 
weather,  and  from  the  liability  of  the  self-acting  cock  to  get 
out  of  order. 

Pig.  68  shows  the  ordinary  arrangements  of  a  cistern  for 
a  dwelling-house.  The  common  material  for  the  cistern  itself 
is  wood  lined  with  sheet  lead  ;  but  slate  cisterns  have  been 
much  used  of  late.  Large  cisterns  or  tanks  for  the  supply 
of  breweries,  manufactories,  &c.,  are  usually  made  of  cast- 
iron  plates,  screwed  together  by  means  of  flanges  all  round 
their  edges. 

The  service  or  feed  pipe  for  a  cistern,  in  the  case  of  an 


ART  OF  BUILDING. 


mtermittent  supply,  must  be  sufficiently  large  to  allow  of 
j^-^  its  filling  during  the  time  the  water 

tt*,»,*r»u„.=  is  turned  on  from  the  mains.  The 


The  service  pipes  to  the  different  parts  of  the  building  are 
laid  into  the  bottom  of  the  cistern,  but  should  not  come 
within  an  inch  of  the  actual  bottom,  in  order  that  the  sedi- 
ment, which  is  always  deposited  in  a  greater  or  less  degree, 
may  not  be  disturbed  :  the  mouth  of  each  pipe  should  be 
covered  by  a  rose,  to  prevent  any  foreign  substances  being 
washed  into  the  pipes  and  choking  the  taps. 

To  afford  a  ready  means  of  cleaning  out  the  cistern,  a 
waste  pipe  is  inserted  quite  at  the  bottom,  sufficiently  large 
to  draw  off  the  whole  contents  in  a  short  time  when  required  ; 
into  this  waste  pipe  is  fitted  a  standing  waste,  which  reaches 
nearly  to  the  top  of  the  cistern,  and  carries  off  the  waste 
water,  when,  from  any  derangement  in  the  working  of  the 
ball  cock,  the  water  continues  running  after  the  cistern  is 
full.  To  prevent  any  leakage  at  the  bottom  of  the  standing 
waste,  the  latter  terminates  in  a  brass  plug,  which  is  ground 
to  fit  a  washer  inserted  at  the  top  of  the  waste  pipe. 

Where  the  supply  of  water  is  constant,  instead  of  being 
intermittent,  private  cisterns  may  be  altogether  dispensed 
with  ;  the  main  service  pipes,  not  beicg  required  to  discharge 
a  large  quantity  of  water  in  a  short  time,  may  be  of  smaller 
bore,  and,  consequently,  cheaper,  and  a  considerable  length 
of  pipe  is  saved,  as  the  water  can  be  laid  on  directly  to  tlie 
several  taps,  instead  of  having  to  be  taken  up  to  the  cistern 
and  then  brought  back  again.  The  constant  flow  of  water 
through  the  pipes  also  much  diminishes  the  risk  of  their 
bursting  in  frosty  weather  from  freezing  of  their  contents. 


^AIN  SERVICE 


3]  flow  of  water  into  the  cistern  is 
g  regulated  by  a  hall  cock,  so  called 
%  from  its  being  opened  and  shut  by 
a  lever,  with  a  copper  ball,  which 
\    floats  on  the  surface  of  the  water. 


80 


RUDIMENTS  OF  THE 


WARMING  AND  VENTILATION. 

13T.  The  various  contrivances  employed  for  warming  build- 
ings may  be  classed  as  under  : — 

Methods  of  Warming  independently  of  Ventilation, 

1st.  By  close  stoves,  the  heating  surface  being  either  of 
iron  or  of  earthenware 

2d.  By  hot-air  flues,  passing  under  the  floors. 

3d.  By  a  system  of  endless  piping  heated  by  a  current  of 
hot  water  from  a  boiler,  the  circulation  being  caused  by  the 
cooling,  and  consequently  greater  weight,  of  tlie  water  in  the 
lower  or  returning  pipe. 

Methods  of  Warming  combined  with  Ventilation,  . 

4th.  By  open  fires  placed  in  the  several  apartments. 

5th.  By  causing  air  w^hich  has  been  previously  heated  to 
pass  through  the  several  rooms.  This  last  system  is  more 
perfect  than  any  of  the  others  abova  described,,  both  as 
regards  economy  of  fuel  and  regulation  of  the  temperature. 

A  great  though  common  defect  in  the  construction  of 
fire-places  is  their  being  placed  too  high  ;  whence  it  is  not 
unusual  for  the  upper  part  of  a  room  to  be  quite  warm  whilst 
there  is  a  stratum  of  cold  air  next  the  floor^  the  effect  of 
which  is  very  injurious  to  health. 

In  all  methods  of  warming,  in  which  the  air  is  heated  by 
coming  in  contact  with  metallic  heating  surfaces,  care  should 
be  taken  that  their  temperature  should  not  exceed  212^  ;  as, 
when  this  limit  is  exceeded,  the  air  becomes  unfit  for  use,  and 
offensive  from  the  scorching  of  the  particles  of  dust  or  other 
matters  that  are  always  floating  in  it. 

138.  There  are  two  modes  in  which  artificial  ventilation  is 
effected,  each  of  which  is  very  efficient. 

The  one  most  in  use  is  to  establish  a  draught  in  an 


ART  OF  BUILDING. 


81 


Bhaft  or  chimney  communicating  by  flues  with  the  apartments 
to  be  ventilated,  the  effect  of  which  is  to  cause  a  constant 
current  in  the  direction  of  the  shaft,  the  air  being  admitted 
at  the  bottom  of  the  building,  and  warmed  or  cooled  as  may 
be  required,  according  to  the  season  of  the  year. 

The  new  House  of  Lords  is  ventilated  in  this  manner.  The 
air  is  admitted  at  the  bottom  of  the  buildings,  filtered  by 
being  passed  through  fine  sieves,  over  which  a  stream  of 
water  is  constantly  flowing  ;  warmed  in  cold  weather  by 
passing  through  steam  cockles,  and  then,  rising  through  the 
building,  goes  out  through  the  roof  into  the  furnace  chimney, 
the  draught  being  assisted  by  a  steam  jet  from  a  boiler. 

139.  The  other  mode  of  ventilation  to  which  we  have 
alluded  is  on  a  completely  opposite  principle  to  that  just 
described,  the  air  being  forced  into  the  apartments  by 
mechanical  means,  instead  of  being  drawn  from  them  by  the 
draught  in  the  chimney. 


82 


RUDIMENTS  OF  THE 


SECTION  11. 

MATERIALS  USED  IN  BUILDING. 

140.  The  materials  used  in  building  may  be  classed  under 
the  following  heads,  viz  : 

Timber,  Stone,  Slate,  Bricks  and  Tiles,  Limes  and  Cements, 
Metals,  Glass,  Colors  and  Yarnishes. 

TIMBER. 

141.  If  we  examine  a  transverse  section  of  the  stem  of  a 
tree,  we  perceive  it  to  consist  of  three  distinct  parts  :  the 
hark^  the  wood,  and  the  fith.  The  wood  appears  disposed  in 
rings  round  the  pith,  the  outer  rings  being  softer  and  con- 
taining more  sap  than  those  immediately  round  the  pith  which 
form  what  is  called  the  heart  wood. 

These  rings  are  also  traversed  by  rays  extending  from  the 
centre  of  the  stem  to  the  bark,  called  medullary  rays. 

The  whole  structure  of  a  tree  consists  of  minute  vessels 
and  cells,  the  former  conveying  the  sap  through  the  wood  in 
its  ascent,  and  through  the  bark  to  the  leaves  in  its  de- 
scent ;  and  the  latter  performing  the  functions  of  secretion 
and  nutrition  during  the  life  of  the  tree.  The  solid  parts  of 
a  tree  consist  almost  entirely  of  the  fibrous  parts  composing 
the  sides  of  the  vessels  and  cells. 

By  numerous  experiments  it  has  been  ascertained  that  the 
sap  begins  to  ascend  in  the  spring  of  the  year,  through  the 
minute  vessels  in  the  wood,  and  descends  through  the  bark 
to  the  leaves,  and,  after  passing  through  them,  is  deposited 
in  an  altered  state  between  the  bark  and  the  last  years's 
wood,  forming  a  new  layer  of  bark  and  sap  wood,  the  old 
bark  being  pushed  forward. 

As  the  annual  layers  increase  in  number,  the  sapwood 


AIIT  OF  BUILDING. 


83 


ceases  to  perforin  its  original  functions  ;  the  fluid  parts  are 
evaporated  or  absorbed  by  the  new  wood,  and,  the  sides  of 
the  vessels  being  pressed  together  by  the  growth  of  the  lat- 
ter, the  sap  wood  becomes  heart  wood  or  perfect  wood,  and 
until  this  change  takes  place  it  is  unfit  for  the  purposes  of 
the  builder. 

The  vessels  in  each  layer  of  wood  are  largest  on  the 
side  nearest  the  centre  of  the  stem,  and  smallest  at  the  out- 
side. This  arises  from  the  first  being  formed  in  the  spring, 
when  vegetation  is  most  active.  The  oblong  cells  which 
surround  the  vessels  are  filled  with  fluids  in  the  early  growth ; 
but,  as  the  tree  increases  in  size,  these  become  evaporated 
and  absorbed,  and  the  cells  become  partly  filled  with  depo- 
sitions of  woody  matter  and  indurated  secretions,  depending 
on  the  nature  of  the  soil,  and  affecting  the  quality  of  the 
timber.  Thus  Honduras  mahogany  is  full  of  black  specks, 
Mdiile  the  Spanish  is  full  of  minute  white  particles,  giving 
the  wood  the  appearance  of  having  been  rubbed  over  with 
chalk.  At  a  meeting  of  the  Institution  of  Civil  Engineers, 
March,  1842,  it  was  stated  by  Professor  Brande,  that  "  a 
beech  tree  in  Sir  John  Sebright^s  park  in  Hertfordshire,  on 
being  cut  down,  was  found  perfectly  black  all  up  the  heart. 
On  examination  it  was  discovered  that  the  tree  had  grown 
upon  a  mass  of  iron  scoriae  from  an  ancient  furnace,  and  that 
the  wood  had  absorbed  the  salt  of  iron."  This  anecdote  well 
explains  the  differences  that  exist  between  different  specimens 
of  the  same  kind  of  timber  under  different  circumstances  of 
growth  ;  and  it  is  probably  the  nature  of  the  soil  that  causes 
the  difference  of  character  we  have  just  named  between  Hon- 
duras and  Spanish  mahogany. 

There  is  a  great  difference  in  the  character  of  the  annual 
rings  in  different  kinds  of  trees.  In  some  they  are  very  dis- 
tinct, the  side  next  the  heart  being  porous,  and  the  other 
being  compact  and  hard,  as  the  oak,  the  ash,  and  the  elm. 
In  others  the  distinctions  between  the  rings  is  so  small  as 
scarcely  to  be  distinguished,  and  the  texture  of  the  wood  is 


RUDISrENTS  OF  THE 


•nearly  uniform,  as  in  the  beech  and  mahogany.  A  third 
class  of  trees  haye  the  annual  rings  very  distinct  and  their 
pores  filled  with  resinous  matter,  one  part  being  hard  and 
heavy,  the  other  soft  and  light-colored.  All  the  resinous 
woods  have  this  character,  as  larch,  fir,  pine,  and  cedar. 

The  medullary  rings  are  scarcely  perceptible  to  the  naked 
eye  in  the  majority  of  trees  ;  but  in  some,  as  the  oak  and 
the  beech,  there  are  both  large  and  small  rings,  which,  when 
cut  through  obliquely,  produced  the  beautiful  flowered  ap- 
pearance called  the  silver  grain. 

142.  In  preparing  timber  for  the  uses  of  the  builder  there 
are  three  principal  things  to  be  attended  to,  viz.,  the  age  of 
the  tree,  the  time  of  felling,  and  the  seasoning  for  use. 

143.  If  a  tree  be  felled  before  it  is  of  full  age,  whilst  the 
heartwood  is  scarcely  perfected,  the  timber  will  be  of  inferior 
quality,  and,  from  the  quantity  of  sap  contained  in  it,  will 
be  very  liable  to  decay.  On  the  other  hand,  if  the  tree  be 
allowed  to  stand  until  the  heartwood  begins  to  decay,  the 
timber  will  be  weak  and  brittle  :  the  best  timber  comes  from 
trees  that  have  nearlv  done  growing,  as  there  is  then  but 
little  sapwood,  and  the  heartwood  is  in  the  best  condition. 

144.  The  best  time  for  felling  trees  is  either  in  mid-winter, 
when  the  sap  has  ceased  to  flow,  or  in  mid-summer,  when  the 
sap  is  temporarily  expended  in  the  production  of  leaves.  An 
excellent  plan  is  to  bark  the  timber  in  the  spring  and  fell  it 
in  winter,  by  which  means  the  sapwood  is  dried  up  and  har- 
dened ;  but  as  the  bark  of  most  trees  is  valueless,  the  oak 
tree  (whose  bark  is  used  in  tanning.^  is  almost  the  only  one 
that  will  pay  for  being  thus  treated. 

145.  The  seasoning  of  timber  consists  in  the  extraction  or 
evaporation  of  the  fluid  parts,  which  are  liable  to  decompo- 
sition on  the  cessation  of  the  growth  of  the  tree.  This  is 
usually  effected  by  steeping  the  green  timber  in  water,  to 
dilute  and  wash  out  the  sap  as  much  as  possible,  and  then 


ART  OF  BUILDING. 


85 


drying  it  thoroughly  by  exposure  to  the  air  in  an  airy  situ- 
ation. The  time  required  to  season  timber  thoroughly  in 
this  manner  will  of  course  much  depend  on  the  sizes  of  the 
pieces  to  be  seasoned  ;  but  for  the  general  purposes  of  car- 
pentry, two  years  is  the  least  that  can  be  allowed,  and,  in 
seasoning  timber  for  the  use  of  the  joiner,  a  much  longer 
time  is  usually  required. 

146.  Decay  of  Timber. — Properly  seasoned  timber,  placed 
in  a  dry  situation  with  a  free  circulation  of  air  round,  it  is 
very  durable,  and  has  been  known  to  last  for  several  hun- 
dred years  without  apparent  deterioration.  This  is  not, 
however,  the  case  when  exposed  to  moisture,  which  is  al- 
ways more  or  less  prejudical  to  its  durability. 

When  timber  is  constantly  under  water,  the  action  of  the 
water  dissolves  a  portion  of  its  substance,  which  is  made  ap- 
parent by  its  becoming  covered  with  a  coat  of  slime.  If  it 
be  exposed  to  alternations  of  dryness  and  moisture,  as  in  the 
case  of  piles  in  tidal  waters,  the  dissolved  parts  being  con- 
tinually moved  by  evaporation  and  the  action  of  the  water, 
new  surfaces  are  exposed,  and  the  wood  rapidly  decays. 

Where  timber  is  exposed  to  heat  and  moisture,  the  albu- 
men or  gelatinous  matter  in  the  sapwood  speedily  putrefies 
and  decomposes,  causing  what  is  called  rot.  The  rot  in  tim- 
ber is  commonly  divided  into  two  kinds,  the  wet  and  the  dry^ 
but  the  chief  difference  between  them  is,  that  where  the  tim- 
ber is  exposed  to  the  air,  the  gaseous  products  are  freely 
evaporated  ;  whilst,  in  a  confined  situation,  they  combine  in 
a  new  form,  viz.,  the  dry-rot  fungus,  which,  deriving  its 
nourishment  from  the  decaying  timber,  often  grows  to  a 
length  of  many  feet,  spreading  in  every  direction,  and  insinu- 
ating its  delicate  fibres  even  through  the  joints  of  brick 
walls. 

In  addition  to  the  sources  of  decay  above  mentioned,  tim- 
ber placed  in  sea-water  is  very  liable  to  be  completely  de- 
stroyed by  the  perforations  of  the  worm,  unless  protected  by 


86 


EUDIMENTS  OF  THE 


copper  sheathing,  the  expense  of  which  causes  it  to  be  seldom 
used  for  this  purpose. 

14  T.  Prevention  of  Decay. — The  best  method  of  protecting 
woodwork  from  decay  when  exposed  to  the  weather  is  to 
paint  it  thoroughly,  so  as  to  prevent  its  being  affected  by 
moisture.  It  is,  however,  most  important  not  to  apply  paint 
to  any  woodwork  which  has  not  been  thoroughly  seasoned  ; 
for  in  this  case  the  evaporation  of  the  sap  being  prevented, 
it  decomposes,  and  the  wood  rapidly  decays. 

Many  plans  have  been  proposed  for  preventing  the  rot. 

148.  For  a  list  of  the  varieties  of  timber  for  building  pur- 
poses, see  Appendix. 

149.  For  internal  finishings,  mahogany  is  much  used  ; 
that  called  Spanish,  which  comes  from  the  West  India 
Islands  is  considered  the  best. 

For  joiners'  and  cabinet  makers' work,  a  great  many  kinds 
of  fancy  wood  are  imported,  which  are  cut  by  machinery 
into  thin  slices,  called  verteers^  and  used  as  an  ornamental 
covering  to  inferior  work.  In  veneering  care  should  be 
taken  that  the  body  of  the  work  be  thoroughly  seasoned,  or 
it  will  shrink,  and  the  veneer  fly  off. 

LIMES  AND  CEMENTS,  MORTAR,  ETC. 

150.  So  much  of  the  stability  of  brickwork  and  masonry 
depends  upon  the  binding  properties  of  the  mortar  or  cement 
with  which  the  materials  are  united,  especially  when  exposed 
to  a  side  pressure,  as  in  the  case  of  retaining  walls,  arches, 
and  piers,  that  it  is  of  no  small  importance  to  ascertain  on 
what  the  strength  of  mortar  really  depends,  and  how  far  the 
proportions  of  the  ingredients  require  modification,  according 
to  the  quality  of  the  lime  that  may  have  to  be  used. 

It  was  long  supposed  that  the  hardness  of  any  mortar  de« 
pended  upon  the  hardness  of  the  limestone,  from  which  the 


ART.  OF  BUILDING.  81 

lime  used  in  its  composition  was  derived  ;  but  it  was  ascer- 
tained by  tiie  celebrated  Smeaton,  and  since  his  time  clearly 
shown  by  the  researches  of  others,  amongst  whom  may  be 
named,  Vicat  in  France,  and  Colonel  Pasley  in  England, 
that  the  hardness  of  the  limestone  has  nothing  to  do  with 
the  matter,  and  that  it  is  its  chemical  composition  which 
regulates  the  quality  of  the  mortar. 

151.  Limestone  may  be  divided  into  three  classes  : 
1st.  Pure  limes — as  chalk. 

2d.  Water  limes — some  of  which  are  only  slightly  hy- 
draulic, as  the  stone  limes  of  the  lower  chalk,  whilst  others 
are  eminently  so,  as  the  lias  limes. 

3d  Water  cements — as  those  of  Sheppy  and  Harwich. 

152.  In  making  mortar  the  following  processes  are  gone 
through  : 

1st.  The  limestone  is  calcined  by  exposure  to  strong 
heat  in  a  kiln,  which  drives  off  the  carbonic  acid  gas  con- 
tained in  it,  and  reduces  it  to  the  state  of  quick-lime. 

2d.  The  quick-lime  is  slaked  by  pouring  water  upon  it, 
when  it  swells,  more  or  less,  with  considerable  heat,  and 
falls  into  a  fine  powder,  forming  a  hydrate  of  lime. 

3d.  The  hydrate  thus  formed  is  mixed  up  into  a  stiiBfish 
paste,  with  the  addition  of  more  water,  and  a  proper  pro- 
portion of  sand,  and  is  then  ready  for  use. 

153.  Pure  Limes. — Chalk  is  a  pure  carbonate  of  lime, 
consisting  of  about  5  parts  of  lime  combined  with  4  of  car- 
bonic acid  gas.  It  expands  greatly  in  slaking,  and  will  bear 
from  three  to  3  J  parts  of  sand  to  one  of  lime,  when  made  up 
into  mortar.  Chalk  lime  mortar  is,  however,  of  little  value, 
as  it  sets  or  hardens  very  slowly,  and  in  moist  situations 
never  sets  at  all,  but  remains  in  a  pulpy  state,  which  renders 
it  quite  unfit  for  any  work  subjected  to  the  action  of  water, 
or  even  for  the  external  walls  of  a  building. 


88 


RUDIMENTS  OF  THE 


154.  Gypsum,  from  which  is  made  plaster  of  Paris  for 
cornices  and  internal  decorations,  is  granular  sulphate  of 
lime,  and  contains  26*5  of  lime,  3t'5  of  sulphuric  acid,  and 
It  of  water.  It  slakes  without  swelling,  with  a  moderate 
heat,  setting -hard  in  a  very  short  time,  and  will  even  set 
under  water  ;  but  as  it  is,  like  other  pure  limes,  partly  solu- 
ble in  water,  it  is  not  suitable  for  anything  but  internal 
work. 

155.  Water  limes  have  obtained  their  name  from  the  ptO- 
perty  they  possess,  in  a  greater  or  less  degree,  of  setting 
under  water.  They  are  composed  of  carbonate  of  lime, 
mixed  with  silica,  alumina,  oxide  of  iron,  and  sometimes 
other  substances. 

156.  Dorking  lime,  obtained  from  the  beds  of  the  lower 
chalk,  at  Dorking,  in  Surrey  ;  and  Hailing  lime,  from  a 
similar  situation  near  Rochester,  in  Kent,  are  the  principal 
limes  used  in  London  for  making  mortar,  and  are  slightly 
hydraulic  ;  they  expand  considerably  in  slaking,  but  not  so 
much  as  the  pure  limes,  and  will  make  excellent  mortar  when 
mixed  with  three  parts  of  sand  to  one  of  lime.  Mortar  made 
with  these  limes  sets  hard  and  moderately  quick,  and  when 
set,  may  be  exposed  to  considerable  moisture  without  injury  ; 
but  they  will  not  set  under  water,  and  are  therefore  unfit  for 
hydraulic  works,  unless  combined  with  some  other  substance, 
as  puzzolanaj  to  give  them  water-setting  properties. 

157.  The  blue  lias  limes  are  the  strongest  water  limes  in 
this  country.  They  slake  very  slowly,  swelling  but  little  in 
the  process,  and  set  very  rapidly  even  under  water  ;  a  few 
days  only  sufficing  to  make  mortar  extremely  hard.  The 
lias  limes  will  take  a  much  smaller  proportion  of  sand  than 
the  pure  limes,  the  reason  of  which  will  be  understood,  when 
it  is  remembered  that  they  contain  a  considerable  proportion 
of  silica  and  alumina,  combined  with  the  lime  in  their  natu- 
ral state,  and  consequently  the  proportion  of  sand  which 


ART  OF  BUILDING. 


89 


makes  good  mortar  with  chalk  lime,  would  ruin  mortar 
made  with  lias  limes. 

In  the  Yale  of  Belvoir,  where  the  lias  lime  is  extensively 
used,  the  common  practice  is  to  use  equal  parts  of  lime  and 
sand  for  inside,  and  half  sand  to  one  of  lime  for  face  work. 

158.  Water  Cements. — These  differ  from  the  water  limes, 
as  regards  their  chemical  composition,  only  in  containing 
less  carbonate  of  lime  and  more  of  silica  and  alumina.  They 
require  to  be  reduced  to  a  fine  powder  after  calcination, 
without  which  preparation  they  cannot  be  made  to  slake. 
The  process  of  slaking  is  not  accompanied  by  any  increase 
of  bulk,  and  they  set  under  water  in  a  short  time,  a  few 
hours  sufficing  for  a  cement  joint  to  become  perfectly  hard. 

Cement  will  not  bear  much  sand  without  its  cementitious 
properties  being  greatly  weakened,  the  usual  proportion 
being  equal  parts  of  sand  and  cement. 

159.  The  use  of  natural  cement  was  introduced  by  Mr. 
Parker,  who  first  discovered  the  properties  of  the  cement- 
stone  in  the  Isle  of  Sheppy,  and  took  out  a  patent  for  the 
sale  of  it  in  1796,  under  the  name  of  Roman  cement. 

Before  that  time,  hydraulic  mortar,  for  dock  walls,  har- 
bor work,  &c.,  was  usually  made,  by  mixing  common  lime 
with  trass,  from  Andernach  in  Germany,  or  with  puzzolana 
from  Italy  ;  both  are  considered  to  be  volcanic  products, 
the  latter  containing  siUca  and  alumina,  with  a  small  quan- 
tity of  lime,  potash,  and  magnesia.  Iron  is  also  associated 
with  it  in  a  magnetic  state. 

160.  The  expense  of  natural  puzzolana  led  to  the  manu- 
facture of  artificial  puzzolana,  which  appears  to  have  been 
used  at  an  early  date  by  the  Romans,  and  has  continued  in 
use  in  the  south  of  Europe  to  the  present  day  ;  artificial 
puzzolana  is  made  of  pounded  bricks  or  tile  dust.  The 
Dutch  manufacture  an  artificial  puzzolana  from  burnt  clay, 


90 


RUDIMENTS  OF  THE 


in  imitation  of  the  trass  of  Andernach,  which  is  said  to  be  a 
close  imitation  of  the  natural  product. 

161.  The  great  and  increasing  demand  for  cement,  and 
its  great  superiority  for  most  purposes  over  lime  mortar, 
have  induced  manufacturers  to  turn  their  attention  to  the 
manufacture  of  artificial  cement,  and  this  has  been  attended 
in  many  instances  with  perfect  success  ;  the  artificial  cements 
now  offered  for  sale,  formed  by  imitating  the  composition  of 
the  natural  cement-stones,  being  mostly  equal  in  quality,  if 
not  superior,  to  the  Roman  cement,  the  use  of  which  has 
been  partly  superseded  by  them. 

162.  The  quality  of  the  sand  used  in  making  mortar  is  by 
no  means  unimportant.  It  should  be  clean  and  sharp  ;  i.  e., 
angular,  and  perfectly  free  from  all  impurities.  The  purer 
the  lime  the  finer  should  be  the  quality  of  the  sand,  the  pure 
limes  requiring  finer,  and  the  cements  a  coarser  sand,  than 
the  hydraulic  limes. 

CONCRETE  AND  BETON. 

163.  Rubble  masonry,  formed  of  small  stones  bedded  in 
mortar,  appears  to  have  been  commonly  used  in  England 
from  an  early  period ;  and  similar  work,  cemented  with 
hydraulic  mortar,  was  constantly  made  use  of  by  the  Ro- 
mans in  their  sea-works,  of  which  many  remains  exist  at  the 
present  day  in  a  perfectly  sound  state. 

164.  This  mode  of  forming  foundations,  in  situations  where 
solid  masonry  would  be  inapplicable,  has  been  revived  in 
modern  times  ;  in  England  and  the  United  States  under  the 
name  of  concrete,  and  on  the  continent  under  the  name  of 
beton.  Although  very  similar  in  their  nature  and  use,  there 
are  yet  great  differences  between  beton  and  concrete,  which 
depend  on  the  nature  of  the  lime  used,  concrete  being  made 
with  the  weak  water  limes  which  will  not  set  under  water, 
whilst  beton  is  invariably  made  with  water-setting  limes,  or 


ART  OF  BUILDING. 


91 


with  limes  rendered  hydraulic  by  the  addition  of  puzzolana. 
Describing  the  two  by  their  differences,  it  may  be  observed 
that  concrete  is  made  with  unslaked  lime,  and  immediately 
thrown  into  the  foundation  pit ;  be  ton  is  allowed  to  stand 
before  use,  until  the  lime  is  thoroughly  slaked  ;  concrete  is 
thrown  into  its  place  and  rammed  to  consolidate  it  ;  beton 
is  generally  lowered  and  not  afterwards  disturbed  ;  concrete 
must  be  thrown  into  a  dry  place,  and  not  exposed  to  the 
action  of  water  until  thoroughly  set  ;  beton,  on  the  contrary, 
is  made  use  of  principally  under  water ^  to  save  the  trouble 
and  expense  of  laying  dry  the  bottom. 

165.  Concrete  is  usually  made  with  gravel,  sand,  and 
ground  unslaked  lime,  mixed  together  with  water,  the  pro- 
portions of  sand  and  lime  being  those  which  would  make 
good  mortar  without  the  gravel,  and,  of  course,  varying  ac- 
cording to  the  quality  of  the  lime  ;  with  the  common  limes, 
slaking  takes  place  at  the  time  of  mixing,  and  the  quality  of 
the  concrete  is  all  the  better  for  the  freshness  of  the  lime. 
If  lias  lime  be  used,  the  concrete  becomes  beton,  and  must 
be  treated  accordingly. 

The  lime  in  this  case  must  be  thoroughly  slaked  (which 
often  takes  many  hours)  before  it  can  be  considered  fit  for 
use  ;  and,  if  this  precaution  be  not  attended  to,  the  whole 
of  the  work,  after  having  set  very  hard  on  the  surface,  cracks 
and  becomes  a  friable  mass,  from  the  slaking  of  the  refactory 
particles  after  the  body  of  the  concrete  has  set. 

166.  Asphalte,  so  much  in  use  at  the  present  day  for  foot- 
pavements,  terrace-roofs,  &c.,  is  made  by  melting  the  asphalte 
rock,  w^hich  is  a  carbonate  of  lime  intimately  combined  with 
bitumen,  and  adding  to  it  a  small  portion  of  mineral  tar, 
which  forms  a  compact  semi-elastic  solid,  admirably  adapted 
for  resisting  the  effects  of  frost,  heat,  and  wet. 

Many  artificial  asphaltes  have  been  brought  under  public 
notice  from  time  to  time,  but  they  are  all  inferior  to  the  na- 
tural asphalte,  in  the  intimate  combination  of  the  lime  and 


92 


RUDIMENTS  OF  THE 


bitumen,  which  it  appears  impossible  to  effect  thoroughly 
by  artificial  means. 

METALS. 

167.  The  metals  used  as  building  materials  are  iron,  lead, 
copper,  zinc,  and  tin. 

168.  Iron. — Iron  is  used  by  the  builder  in  two  different 
states,  viz.,  cast  iron  and  wrought  iron,  the  differences  be- 
tween them  depending  on  the  proportion  of  carbon  com- 
bined with  the  metal ;  cast  iron  containing  the  most,  and 
wrought  iron  the  least. 

169.  Previous  to  the  middle  of  the  last  century,  the  smelt- 
ing of  iron  was  carried  on  with  wood  charcoal,  and  the  ores 
used  were  chiefly  from  the  secondary  strata,  although  the 
clay  ironstones  of  the  coal  measures  were  occasionally  used. 

110.  The  introduction  of  smelting  with  pitcoal  coke  dur- 
ing the  last  century  caused  a  complete  revolution  in  the  iron 
trade.  The  ores  now  chiefly  used  are  the  clay  ironstones  of 
the  coal  measures,  and  the  fuel,  pitcoal,  or  coke.  Steam 
power  is  almost  exclusively  used  for  the  production  of  the 
blast  in  the  furnaces,  and  for  working  the  forge  hammers  and 
rolling  mills. 

111.  For  the  production  of  wrought  iron  in  the  ordinary 
manner,  two  distinct  sets  of  processes  are  required.  1st. 
The  extraction  of  the  metal  from  the  ore  in  the  shape  of 
cast  iron.  2nd.  The  conversion  of  cast  iron  into  malleable 
or  bar  iron,  by  re-melting,  puddling,  and  forging.  The 
conversion  of  bar  iron  into  steel  is  effected  by  placing  it  in 
contact  with  powdered  charcoal  in  a  furnace  of  cementation. 

112.  Cast  iron  is  produced  by  smelting  the  previously  cal- 
cined ore  in  a  blast  furnace,  with  a  portion  of  limestone  as 
a  flux,  and  pitcoal  or  coke  as  fuel.  The  melted  metal  sinks 
to  the  bottom  of  the  furnace  by  its  greater  specific  gravity. 


ART  OF  BUILDING. 


93 


The  limestone  and  other  hnpurities  float  on  the  top  of  the 
melted  mass,  and  are  allowed  to  run  off,  forming  slag  or 
cinder.  The  melted  metal  is  run  off  from  the  bottom  of  the 
furnace  into  moulds,  where  castings  are  required,  and  into 
furrows  made  in  a  level  bed  of  sand,  when  the  metal  is  re- 
quired for  conversion  into  malleable  iron,  the  bars  thus  pro- 
duced being  called  jpigs. 

113.  In  the  year  182T,  it  was  discovered  that  by  the  use 
of  heated  air  for  the  blast,  a  great  saving  of  fuel  could  be 
effected  as  compared  with  the  cold  blast  process. 

The  hot  blast  is  now  very  extensively  in  use,  and  has  the 
double  advantage  of  requiring  less  fuel  to  bring  down  an 
equal  quantity  of  metal,  and  of  enabling  the  manufacturer 
to  use  raw  pitcoal  instead  of  coke,  so  that  a  saving  is  effect- 
ed both  in  the  quantity  and  cost  of  the  fuel. 

For  a  considerable  time  after  its  introduction  it  was  held 
in  great  disrepute,  which,  however,  may  be  chiefly  attributed 
to  the  inferior  quality  of  materials  used,  the  power  of  the 
hot  blast  in  reducing  the  most  refractory  ores  offej^ing  a 
great  temptation  to  obtain  a  much  larger  product  from  the 
furnace  than  was  compatible  with  the  good  quality  of  the 
metal.  The  use  of  the  hot  blast  by  firms  of  acknov/ledged 
character  has  greatly  tended  to  remove  the  prejudice  against 
it ;  and  in  many  iron  works  of  high  character,  nothing  but 
the  hot  blast  with  pitcoal  is  used  in  the  smelting  furnaces, 
the  use  of  coke  being  confined  to  the  subsequent  processes. 

Perhaps  it  may  be  laid  down  as  a  general  principle,  that 
where  the  pig  iron  is  re-melted  with  coke  in  the  cupola  fur- 
nace, for  the  purposes  of  the  iron  founder  ;  or  refined  with 
coke  in  the  conversion  of  forge  pig  into  bar  iron,  it  is  of  lit- 
tle consequence  whether  the  reduction  of  the  ore  has  been 
effected  with  the  hot  or  the  cold  blast  ;  but  where  castings 
have  to  be  run  directly  from  the  smelting  furnace,  the  quality 
of  the  metal  will,  no  doubt,  suffer  from  the  use  of  the  former. 

174.  Cast  iron  is  divided  by  ironfounders  into  three  qua- 


94 


RUDIMENTS  OF  THE 


lities.  "No.  1,  or  Mack  cast  iron,  is  coarse-grained,  soft,  and 
not  very  tenacious.  When  re-melted  it  passes  into  No.  2, 
or  grey  cast  iron.  This  is  the  best  quality  for  castings  re- 
quiring strength  :  it  is  more  finely  grained  than  No.  1,  and 
is  harder  and  more  tenacious.  When  repeatedly  re-melted 
it  becomes  excessively  hard  and  brittle,  and  passes  into  No. 
8,  or  white  cast  iron,  which  is  only  used  for  the  commonest 
castings,  as  sash-weights,  cannon-balls,  and  similar  articles. 
White  cast  iron,  if  produced  direct  from  the  ore,  is  an  indi- 
cation of  derangement  in  the  working  of  the  furnace,  and  is 
unfit  for  the  ordinary  purposes  of  the  founder,  except  to  mix 
with  other  qualities. 

175.  Girders  and  similar  solid  articles  are  cast  in  sand 
moulds,  enclosed  in  iron  frames  or  hoxes^  each  mould  requir- 
ing an  upper  and  lower  box.  A  mould  is  formed  by  press- 
ing sand  firmly  round  a  wooden  pattern,  which  is  afterwards 
removed,  and  the  melted  metal  poured  into  the  space  thus 
left  through  apertures  made  for  the  purpose. 

Th^moulds  for  ornamental  work  and  for  hollow  castings 
are  of  a  more  complicated  construction,  which  will  be  better 
understood  from  actual  inspection  at  a  foundry  than  from 
any  written  description. 

Almost  all  irons  are  improved  by  admixture  with  others, 
and,  therefore,  where  superior  castings  are  required  they 
should  not  be  run  direct  from  the  smelting  furnace,  but  the 
metal  should  be  re-melted  in  a  cupola  furnace,  which  gives 
the  opportunity  of  suiting  the  quality  of  the  iron  to  its  in- 
tended use.  Thus,  for  delicate  ornamental  work,  a  soft  and 
very  fluid  iron  will  be  required,  whilst,  for  girders  and  cast- 
ings exposed  to  cross  strains,  the  metal  will  require  to  be 
harder  and  more  tenacious.  For  bedplates  and  castings 
which  have  merely  to  sustain  a  compressing  force,  the  chief 
point  to  be  attended  to  is  the  hardness  of  the  metal. 

Castings  should  be  allowed  to  remain  in  the  sand  until 
cool,  as  the  quality  of  the  metal  is  greatly  injured  by  the 


ART  OF  BUILDING. 


95 


rapid  and  irregular  cooling  which  takes  place  from  exposure 
to  air  if  removed  from  moulds  in  a  red  hot  state,  which  is 
sometimes  done  in  small  foundries  to  economise  room. 

The  Scotch  iron,  which  is  so  much  esteemed  for  hollow 
wares,  and  has  a  beautifully  smooth  surface,  is  much  used 
in  the  United  States.  The  Scotch  iron  is  softer,  runs  closer, 
and  is  used  much  for  plates  which  require  smoothness,  for 
steam-engine  cylinders,  and  work  of  Hke  character,  which 
requires  closeness^  or  soundness;  it  is  also  mixed  with  our  Ame- 
rican iron.  The  Eastern  iron  is  the  best  used  in  the  United 
States  for  positions  requiring  great  strength.  The  iroa 
from  the  West  is  more  like  Scotch. 

The  Welch  iron  is  principally  used  for  conversion  into  bar 
iron. 

176.  The  conversion  of  forge  pig  into  bar  iron  is  effected 
by  a  variety  of  processes,  which  have  for  their  object  the 
freeing  the  metal  from  the  carbon  and  other  impurities  com- 
bined with  it,  so  as  to  produce  as  nearly  as  possible  the  pure 
metal.  We  do  not  purpose  to  enter  in  these  pages  into  any 
of  the  details  of  the  manufacture  of  bar  iron,  or  of  its  con- 
version into  steel,  as  our  business  is  rather  with  the  iron- 
founder  than  the  manufacturer  ;  it  may,  however,  be  proper 
to  state  that  new  processes  have  lately  been  patented,  by 
which  malleable  iron  and  steel  may  be  produced  directly  from 
the  ore,  without  the  use  of  the  smelting  furnace,  a  plan 
which  is  likely  to  be  attended  with  beneficial  results,  both  as 
regards  economy  and  quality  of  metal. 

lit.  Lead. — Lead  is  used  by  the  mason  for  securing  dowels, 
coating  iron  cramps,  and  similar  purposes,  see  section  lY., 
Plumber. 

Lead  is  also  used  by  the  smith  in  fixing  iron  railings,  and 
other  work  where  iron  is  let  into  stone  ;  but  the  use  of  lead 
in  contact  with  iron  is  always  to  be  avoided,  if  possible,  as 
it  has  an  injurious  effect  upon  the  latter  metal,  the  part  la 
contact  with  the  lead  becoming  gradually  softened. 


96 


RUDIMENTS  OF  THE 


The  chief  value  of  lead,  however,  to  the  builder,  is  as  a 
covering  for  roofs,  and  for  lining  gutters,  cisterns,  &c.,  for 
which  uses  it  is  superior  to  any  other  metal.  For  these  pur- 
poses the  lead  is  cast  into  sheets,  and  then  passed  between 
rollers  in  a  flatting-mill^  until  it  has  been  reduced  to  the  re- 
quired thickness. 

Cast-lead  is  often  made  by  plumbers  themselves  from  old 
lea,d  taken  in  exchange  ;  but  it  is  very  inferior  to  the  milled 
lead  of  the  manufacturer,  being  not  so  compact,  and  often 
containing  small  air-holes,  which  render  it  unfit  for  any  but 
inferior  purposes. 

1^8.  Copper. — See  Section  IV.,  Coppersmith. 

119.  Zinc. — See  Section  lY.,  Zincworker. 

180.  Brass  is  an  alloy  of  the  copper  and  zinc,  the  best 
proportions  being  nearly  two  parts  of  copper  to  one  of  zinc. 

181.  Bronze  is  a  compound  of  metal,  composed  of  copper 
and  tin,  to  which  are  sometimes  added  a  little  zinc  and  lead. 

The  best  proportions  for  casting  statues  and  bas-reliefs 
appear  to  be  attained  when  the  tin  forms  about  10  per  cent, 
of  the  alloy. 

By  alloying  copper  with  tin,  a  more  fusible  metal  is  ob- 
tained, and  the  alloy  is  much  harder  than  pure  copper  ;  but 
considerable  management  is  required  to  prevent  the  copper 
from  becoming  refined  in  the  process  of  melting,  a  result 
which  has  frequently  happened  to  inexperienced  founders. 

182.  Bell-metal  is  composed  of  copper  and  tin,  in  the  pro- 
portion of  78  per  cent,  of  the  former  to  22  per  cent,  of  the 
latter. 

183.  Cast  iron  lintels  and  columns  are  in  common  use  in 
our  cities.  Cast  iron  blocks  are  also  frequently  used  for  the 
arches  of  bridges.  Iron  chains  are  used  with  advantage 
under  the  roofs  of  circular  buildings. 


ART  OF  BUILDING. 


91 


STONE, 

184.  Granite  rock  appears  to  have  been  originally  a  fused 
mass,  and  subsequently  to  have  undergone  the  process  of 
crystalli^^ation.  It  is  of  a  granidar  structure,  that  is,  con- 
sisting of  separate  grains  of  different  substances,  united,  ap- 
parently, without  the  aid  of  any  intermediate  matter  or  ce- 
ment. These  substances  are  quartz^  felspar,  and  mica,  each 
of  these  being  a  compound.  The  infinite  variety  of  propor- 
tions in  which  their  several  constituent  elements  are  united 
in  the  mass,  occasions  the  great  diversity  of  color,  and  of 
appearance  of  the  several  kinds  of  granite,  and  also  affects 
in  a  much  more  important  manner  the  enduring  character- 
istics of  this  valuable  material.  Thus,  its  color  varies  from 
light  grey  to  a  dark  tint  closely  resembling  black,  and  is  to 
be  found  of  all  shades  of  red,  and  many  green.  Of  the  con- 
stituents of  granite,  qwartz  is  a  substance  of  a  glassy  appear- 
ance, and  of  a  grey  color,  and  is  composed  of  a  metallic  base 
silicium  and  oxygen  :  felspar  is  also  a  crystalline  substance, 
but  commonly  opaque,  of  a  yellowish  or  pink  color,  com- 
posed of  silicious  and  aluminous  mattter,  with  a  small  pro- 
portion of  lime  and  potash  ;  mica,  a  glittering  substance, 
principally  consists  of  clay  and  flint,  with  a  little  magnesia 
and  oxide  of  iron.  Instead  of  the  mica,  another  substance 
called  kornbknck,  is  found  in  some  granites  ;  hornblende  is  a 
dark  crystalline  substance,  composed  of  flint,  alumina,  and 
magnesia,  besides  a  large  poportion  of  the  black  oxide  of 
iron.  Granites  in  which  hornblende  exists  are  sometimes 
called  Syenite,  having  first  been  found  in  the  island  of  Syene 
in  Egypt. 

185.  Granite  is  found  In  mountain-chains,  and  usually  in 
rugged  outlines,  in  nearly  all  parts  of  Europe  and  America, 
Although  all  granites  are  similar  in  structure,  the  difference 
in  the  proportions  of  its  constituent  substances  occasions 
great  difference  in  its  enduring  and  useful  properties.  Some 

t 


98 


RUDIMENTS  OF  THE 


varieties  are  exceedingly  friable  and  liable  to  decomposition, 
while  others,  including  that  known  as  Sienite,  suffer  but  im- 
perceptibly from  moisture  and  the  atmosphere.  The  com- 
pact nature  of  a  close-grained  granite,  having  the  felspar 
highly  crystallized  and  free  from  stains  or  cracks,  seems  well 
calculated  to  resist  the  effect  of  air  and  water. 

186.  Slate. — The  geologists  recognised  four  kinds  of  slate, 
mica  slate,  talcows  slate,  flinty  slate,  and  common  or  clay  slate. 
Of  these  the  last  only  is  a  material  of  extended  use  in  the 
arts  of  building  and  construction.  Clay  slate,  as  its  name 
implies,  consists  chiefly  of  clay  in  an  indurated  condition, 
and  occasionally  containing  particles  of  mica  and  quartz, 
and  in  some  of  the  coarser  kinds,  grains  of  felspar  and  other 
fragments  of  the  primary  rocks.  In  the  extreme  admixture 
of  these  foreign  substances,  clay  slate  approaches  the  nature 
of  the  rock  known  as  grey  wacke.  The  beds  of  clay  slate 
are  invariably  stratified,  the  thickness  of  the  strata,  how- 
ever, varying  from  a  fraction  of  an  inch  to  many  feet.  Its 
laminar  texture  admits  a  ready  separation  into  thin  plates, 
and  thus  endows  it  with  a  supreme  value  for  roofing  and 
other  purposes,  in  which  great  density  and  comparative  im- 
permeability are  required  to  coexist  with  a  minimum  thick- 
ness and  weight.  The  weight  of  slates  varies  from  174  to 
It 9  lbs.  per  cubic  foot. 

187.  Sandstones. — These  rocks,  belonging,  geologically, 
to  various  positions  in  the  order  of  the  strata  of  which  the 
exterior  of  the  earth  is  composed.  Sandstones  are  princi- 
pally silicious,  and  possess  various  degrees  of  induration. 
These  stones  weigh  from  140  to  150  lbs.  per  cubic  foot. 

188.  From  the  nature  of  the  composition  of  sandstones,  it 
results  that  their  resistance  against,  or  yielding  to,  the  de- 
composing effects  to  which  they  are  subjected,  depends  to  a 
great  extent,  if  not  wholly,  upon  the  nature  of  the  cementing 
substance  by  which  the  grains  are  united ;  these  latter 


ART  OF  BUILDING.. 


99 


being  comparatively  indestructible.  From  the  nature  of 
their  formation,  sandstones  are  usually  laminated,  and  more 
especially  so  when  mica  is  present,  the  plates  of  which  are 
generally  arranged  in  planes  parallel  to  their  beds.  Stones 
of  this  description  should  be  carefully  placed  in  constructions, 
so  that  these  planes  of  lamination  may  be  horizontal,  for  if 
placed  vertically,  the  action  of  decomposition  will  occur  in 
flakes,  according  to  the  thickness  of  the  laminae.  Indeed, 
the  best  way  of  using  all  descriptions  of  stone  is  in  the  same 
position  which  they  had  in  the  quarry  ;  but  this  becomes  an 
imperative  rule  with  those  of  laminated  structure. 

189.  Uniformity  of  color  is  a  tolerably  correct  criterion 
of  uniformity  of  structure,  and  this  constitutes,  other  circum- 
stances being  equal,  one  of  the  practical  excellencies  of 
building  stones.  The  great  injury  occasioned  to  these  ma- 
terials by  their  absorption  of  moisture,  leads  properly  to  a 
preference  for  such  stones  as  resist  its  introduction,  for  all 
above  ground  purposes.  Those  which  imbibe  and  retain 
moisture  are  especially  liable  to  disruption  by  frost,  if  ex- 
posed. The  simplest  method  of  finding  out  the  disposition 
of  stone  to  imbibe  moisture  is  to  immerse  it  for  a  lengthened 
period  of  time  in  water,  and  to  comj)are  the  weight  of  it  be- 
fore and  after  such  immersion. 

190.  Limestones. — The  class  of  hmestones,  including  the 
magnesian  limestones  and  the  oolites,  is  one  of  extreme  im- 
portance in  the  building  arts,  comprehending  some  of  the 
most  advantageous  materials  of  construction,  and  combining 
great  comparative  durability  with  peculiar  facilities  for 
working,  m  which  they  surpass  the  sandstones.  Of  the  lime- 
stones and  the  oolites,  the  principal  material  is  carbonate  of 
lime.  The  magnesian  limestones  contain  a  quantity  o|  Ga¥»^ 
bonate  of  magnesia,  in  some  cases  nearly  equal  to  tha^  of 
carbonate  of  lime. 

191.  It  is  remarked  that  r^agnesian  limestone  appearsi 
capable  of  resisting  deqaniposing  action  in  proportion  as  its 
structure  is  crystalline, 


100 


RUDIMENTS  OF  THE 


SLATE. 

192.  Section  IV. 

GLASS. 

193.  iSeie  Section  IV. 

BRICKS  AND  TILES. 

194.  According  to  the  Bible,  burnt  bricks  were  used  in 
the  Tower  of  Babel. 

In  Egypt,  bricks  were  made  of  clay,  mixed  with  dried 
straw,  and  dried  in  the  sun. 

195.  The  usual  form  of  a  brick  is  a  paralellopipedon, 
about  9  in.  long,  4  J  in.  broad,  and  2^  to  3  in.  thick — the  exact 
size  varying  witli  the  construction  of  the  clay.  The  thick- 
ness need  not  bear  any  definite  proportion  to  the  length  and 
breadth,  but  these  last  dimensions  require  nice  adjustment, 
as  the  length  should  exceed  twice  the  breadth  by  the  thick- 
ness of  a  mortar  joint. 

196.  The  manufacture  of  tiles  is  similar  to  that  of  bricks^ 
the  principal  difference  arising  from  the  thinness  of  the  ware. 

Paving  tiles  may  be  considered  simply  a  thin  brick. 

Roofing  tiles  are  of  two  kinds  :  pantiles,  which  are  of  a 
curved  shape,  and  plaintiles,  which  are  flat,  the  latter  being 
often  made  of  ornamental  shapes  so  as  to  form  elegant  pat- 
terns when  laid  on  a  roof. 

Pantiles  are  moulded  flat,  and  afterwards  bent  into  their 
required  shape  on  the  mould.  Plaintiles  were  formerly  made 
with  holes  in  them  for  the  reception  of  the  tile-pins,  by  which 
they  were  hung  on  the  laths  ;  but  the  common  method  now 
is  to  turn  down  a  couple  of  nibs  at  the  head  of  the  tile, 
which  answer  the  same  purpose. 

19T.  Draining  tiles  are  the  coarsest  kind  of  earthenware. 
They  are  of  various  shapes,  and  are  made  in  various  ways. 

198.  Glass.    See  Section  IV. 

199.  Colors  and  varnishes.    See  Section  IV. 


ART  OF  BUILDING. 


101 


SECTION  TIL 

STRENGTH  OF  MATERIALS. 

200.  There  are  three  principal  actions  to  which  the  ma- 
terials of  a  building  are  exposed. 

1st.  Compression — as  the  case  of  the  stones  in  a  wall. 

2nd.  Tension — as  in  the  case  of  a  king-post  or  tie-beam. 

3rd.  Cross-strain — as  in  the  case  of  a  bressummer,  floor- 
joists,  &c. 

The  last  of  the  three  is  the  only  one  against  which  pre- 
cautions are  especially  necessary,  as  in  all  ordinary  cases  the 
resistance  of  the  materials  used  for  building  is  far  beyond 
any  direct  crushing  or  pulling  force  that  is  likely  to  be 
brought  upon  them. 

201.  1st.  Resistance  to  Comp-ession. — The  following  table 
shows  the  force  required  to  crush  1\  in.  cubes  of  several 
kinds  of  building  material: — 

lbs.  lbs. 

Good  brick  .  .  181t  Portland  stone  .  .  10,284 
Derbyshire  grit  .  7070     Granite  .  .14,300. 

These  amounts  so  far  exceed  any  weight  that  could  have 
to  be  borne  on  an  equal  area,  under  ordinary  circumstances, 
that  it  is  quite  unnecessary  in  the  erection  of  a  building  to 
make  any  calculations  on  this  head  when  using  these  or 
similar  materials. 

Cast  iron  may  be  considered  as  practically  incompressible  ; 
wrought  iron  may  be  flattened  under  great  pressure,  but 
cannot  be  crushed.  Timber  may  be  considered,  for  practical 
purposes,  as  nearly  incompressible,  when  the  weight  is  ap- 
plied in  the  direction  of  the  fibres,  as  in  the  case  of  a  wooden 
story-post ;  but  the  softer  kinds,  as  fir,  offer  little  resistance, 


102 


RUDIMENTS  OF  THE 


when  the  weight  is  applied  at  right  angles  to  the  fibres,  as 
in  the  case  of  the  sill  of  a  partition  ;  and,  beside  this,  timber, 
however  well-seasoned,  will  always  shrink,  more  or  less,  in 
the  direction  of  its  thickness,  so  that  no  important  bearings 
should  be  trusted  to  it. 

202.  2nd.  Resistance  to  Tension. — The  principal  building 
materials  that  are  required  to  resist  direct  tension  are  timber 
and  IV r ought  iron. 

The  following  table  shows  the  weight  in  tons  required  to 
tear  asunder  bars  1  inch  square  of  the  following  materials  : — 


Tons. 

Oak   5  1-6 

Fir  .    .  •   54 

Cast  iron   7| 

Wrought  iron   10 

Wrought  copper   15 

English  bar  iron   25 

American  iron    .    .    .    .    .    .    .  . 

Blistered  steel   59J 


Cast  irony  however,  although  included  in  the  above  table, 
is  an  unsuitable  material  for  the  purpose  of  resisting  tension, 
being  comparatively  brittle.  With  regard  to  timber^  it  is 
practicably  impossible  to  tear  asunder  a  piece  of  even  mo- 
derate size,  by  a  force  applied  in  the  direction  of  the  fibres, 
and  therefore  the  dimensions  of  king-posts,  tie-beams,  and 
other  timbers  whicli  have  to  resist  a  pulling  force,  are  regu- 
lated by  the  necessity  of  forming  proper  joints  and  connec- 
tions with  the  other  parts  of  the  framing  to  which  they  be- 
long, rather  than  by  their  cohesive  strength.  But  it  must 
be  borne  in  mind,  that  although  the  strength  of  all  kinds  of 
timber  is  very  great  in  the  direction  of  the  fibres,  the  lateral 
cohesion  of  the  annual  rings  is  in  many  kinds  of  wood  very 
slight,  and  must  be  assisted  by  iron  straps  in  all  doubtful 
cases.  The  architects  of  the  middle  ages  executed  their 
magnificent  wooden  roofs  without  these  aids,  but  they  worked 


ART  OF  BUILDING. 


lOS 


in  oak,  and  not  in  soft  fir,  which  would  split  and  rend  if  ^ 
treated  in  the  same  way. 

Wrought  iron  is  extensively  used  for  bolts,  straps,  tie-rods, 
and  all  purposes  which  require  great  strength,  with  small 
sectional  area  ;  one-fourth  of  the  breaking  weight  is  usually 
said  to  be  the  limit  to  which  it  should  be  strained  ;  but,  in 
all  probability,  this  amount  might  be  doubled  without  any 
injurious  effects. 


203.  3rd.  Cross  Strain. — In  calculating  the  strength  of 
beams  when  exposed  to  cross  or  transverse  strain,  two  prin- 
cipal considerations  present  themselves:  1st.  The  mechanical 
effect  which  any  given  load  will  produce  under  varying  con- 
ditions of  support:  and  2ndly.  The  resistance  of  the  beam, 
and  the  manner  in  which  this  is  affected  by  the  form  of  its 
section. 

204.  1st.  Mechanical  Effect  of  a  given  Load  under  varying 
Circumstances. — If  a  rectangular  beam  be  supported  at  each 
end  and  loaded  in  the  middle,  the  strength  of  the  beam,  its 
section  remaining  the  same,  will  be  inversely  as  the  distance 
between  the  supports,  the  weight  acting  with  a  leverage 
which  increases  at  this  distance  *    If  a  beam  be  fixed  at  one 


*  It  may  be  as  well  to  observe  that,  although  this  is  true  as  to  the  strength  of 
beams  under  ordinary  circumstances,  it  does  not  hold  good  when  the  loading  is 
carried  to  the  breaking  point,  the  deflection  of  the  beam  causing  an  increase  or 
diminution  of  the  leverage  according  to  the  mode  of  support.  The  difference  of 
strength  arising  from  this  cause  is,  ho^yeve^.,  too  trifling  to  be  taken  into  consider- 
ation, except  in  delicate  experiments  on  the  ultimate  strength  of  beams. 


STRENGTH  OF  BEAMS. 


Fig.  70. 


RUDIMENTS  OF  THE 


end  and  weighted  at  the  other  (fig.  tO),  its  strength  will  be 
half  that  of  a  similar  beam  of  double  the  length  supported 
as  first  described  (fig.  ^1).  A  parallel  case  to  this  is  that 
of  a  beam  supported  in  the  middle  and  loaded  at  the  ends 


Fig.  71. 


(fig.  ([2).  In  each  of  the  above  cases  the  beam  will  bear 
double  the  load  if  it  be  equally  distributed  over  its  whole 


Fig.  72. 


lengthy  as  shown  by  the  dotted  lines  ;  and  lastly,  the  strength 
of  a  beam  firmly  fixed  at  the  ends  is  to  its  strength  wheo 
loosely  laid  on  supports  as  3  to  2  {see  fig.  7S 

Fig.  7S. 


ART  OF  BUILDING* 


105 


These  results  may  be  simply  expressed  thus  : 
Let  5  be  the  weight  which  would  break  a  beam  of  given 
length  and  scantling  fixed  at  one  end  and  loaded  at  the 
other  : 

then  2  s  would  break  the  same  beam  fixed  at  one  end  and 

uniformly  loaded  : 
4  5  would  break  the  same  beam  supported  at  each  end 

and  loaded  in  the  middle  : 
6  s  would  break  the  same  beam  fixed  at  each  end  and 

loaded  in  the  middle  : 
8  s  would  break  the  same  beam  supported  at  each  end 

and  uniformly  loaded  : 
12  5  would  break  the  same  beam  fixed  at  each  end  and 

uniformly  loaded. 

205.  2d.  Resistance  of  the  Beam. — If  a  beam  be  loaded  so 
as  to  produce  fracture,  this  will  take  place  about  a  centre  or 
neutral  axis,  below  which  the  fibres  will  be  torn  asunder,  and 
above  which  they  will  be  crushed.  This  may  be  very  clearly 
illustrated  by  drawing  a  number  of  parallel  lines  with  a  soft 
pencil  on  the  edge  of  a  piece  of  India  rubber,  and  bending 
it  round,  when  it  will  be  seen  that  the  lines  are  brought 
closer  together  on  the  concave,  and  stretched  further  asunder 
on  the  convex  side,  whilst,  between 
"f"^'^'       I         ^^^^       edges,  a  neutral  line  may  be 

  Ill  Hi.  ll  l!      traced,  on  which  t  he  divisions  remain 

of  the  original  size,  which  neutral  line 
divides  the  fibres  that  are  subjected 
to  compression  from  those  in  a  state 
of  tension  {see  fig.  74). 
The  resistance  of  a  rectangular  beam  will,  therefore, 
depend,  1st,  on  the  number  of  fibres,  which  will  be  propor- 
tionate to  its  breadth  and  depth  ;  2d,  on  the  distance  of 
those  fibres  from  the  neutral  axis,  and  the  consequent  lever- 
age with  which  they  act,  which  will  also  be  as  the  depth  ; 
and,  lastly,  on  the  actual  strength  of  the  fibres,  which  will 


106 


RUDIMENTS  OF  THE 


vary  with  different  materials,  and  can  only  be  determined 
approximately  from  actual  experiments  on  rectangular  beams 
of  the  same  material  as  those  whose  strength  is  required  to 
be  estimated. 

The  actual  strength  of  any  rectangular  beam  will,  there- 
fore, be  directly  as  its  breadth  multiplied  by  the  square  of 
the  depth,  and  inversely  as  its  length  ;  or,  calling  s  the 
transverse  strength  of  the  material,  as  in  art.  117,  J  the 
breadth,  d  the  depth,  I  the  length  between  the  supports,  and 
W  the  breaking  weight : 

shd^ 

W  =  . 

I 

The  following  may  be  taken  as  the  value  of  s  for  iron  and 
timber,  the  length  being  taken  in  feet,  the  breadth  and  depth 
in  inches,  and  the  breaking  weight  in  pounds. 

Constant  multiplier  Constant  multiplier 

for  rectangular  beams  for  rectangular  beama 
fixed  at  one  end  and  loosely  supported  at 
loaded  at  the  other.  the  ends  and  loaded 

in  the  middle. 

Wrought  iron  512 )  ( 2048 

Cast  ditto  500  [-      X  4     ]  2000* 

Fir  and  English  oak  )  (  400 

It  must  be  remembered  that  the  numbers  here  given 
indicate  the  breaking  weight,  not  more  than  one-third  of 
which  should  ever  be  applied  in  practice.  Timber  is  per- 
manently injured  if  more  than  even  one-fourth  of  the  break- 
ing weight  is  placed  on  it,  and,  therefore,  this  limit  should 
never  be  passed. 

A  single  example  will  suffice  to  show  the  importance  of 
the  principles  just  explained,  and  the  lamentable  results  that 
may  follow  from  ignorance  of  them.  If  we  take  a  fir  bind- 
ing-joist, say  9  in.  X  4  in.,  which  is  to  have  a  bearing  of 
12  ft.  between  its  supports,  and  place  it  edgeways,  it  will  re- 
quire to  break  it  a  weight  =  400  X  4  X  9^ 

 =10,800  lbs. ; 

12 


*  The  above  is  an  average  value  calculated  from  a  great  number  of  published 
experiments  on  different  irons. 


AKT  OF  BUILDING, 


101 


but  if,  for  the  purpose  of  gaining  height,  we  place  it  flat- 

400  +  9  +  42 

ways,  it  will  break  with  a  weight  =  =  4,800  lbs  , 


12 


or  less  than  one-half. 


206.  We  may  see  from  this  example  that  the  shape  of  any 
beam  has  a  great  influence  on  its  strength  ;  and  in  making 
beams  of  iron,  which  can  be  cast  with  great  facility  in  any 
required  shape,  it  becomes  an  important  question  how  to 
obtain  the  strongest  form  of  section  with  the  least  expendi- 
ture of  metal. 

The  usual  section  given  to  cast-iron  girders  is  that  of 
a  thin  and  deep  rectangular  beam,  with  flanges  or  pro- 
jections on  each  side  at  top  and  bottom  ;  where  the 
strength  of  the  metal  will  be  most  effective,  as  being  at 
the  greatest  possible  distance  from 
the  neutral  axis  (^fig.  78). 

The  great  question  now  is,  what 
should  be  the  relative  thickness  of 
the  top  and  bottom  flanges,  the 
centre  part  of  the  beam  having 
been  made  as  thin  as  is  consistent 
with  sound  casting  ? 
If  the  metal  were  incompressible,  the  top  flanges  might 
be  infinitely  thin  ;  if  incapable  of  extension,  the  bottom 
ones  might  be  indefinitely  reduced.  If  it  offered  equal 
resistance  to  tension  and  compression,  the  neutral  axis  would 
occupy  the  centre  of  the.  beam,  and  the  top  and  bottom 
flanges  would  require  to  be  of  equal  strength. 

We  are  indebted  to  Mr.  Eaton  Hodgkinson  for  the 
publication*  of  a  valuable  set  of  experiments  conducted  by 
him,  having  for  their  object  the  determination  of  the  position 
of  the  neutral  axis  in  cast-iron  beams.    The  result  of  his 


 :VV-  *. 


*  Experimental  Researches  on  the  Strength  and  other  Properties  of  Cast  Iron, 
8vo,  1846.  Weale. 


108 


RUDIMENTS  OF  THE 


experiments  is,  that  in  cast-iron  rectangular  beams,  the 
position  of  the  neutral  axis  at  the  time  of  fracture  is  at  about 
one-seventh  of  the  whole  depth  of  the  beam  below  its  upper 
surface.  Hence,  in  girders  with  flanges,  the  thickness  of 
the  bottom  flanges  should  be  six  times  that  of  the  upper 
ones  ( supposing  them  to  be  of  the  same  width),  in  order  to 
obtain  the  greatest  strength  with  the  least  metaL  Practically 
it  would  be  almost  impossible  to  cast  a  beam  thus  proportioned, 
and,  therefore,  the  top  flanges  are  made  of  the  same  thick- 
ness, or  nearly  so,  as  the  bottom  ones,  but  of  a  less  width, 
so  as  to  contain  the  same  relative  quantity  of  metal,  disr 
posed  in  a  more  convenient  form  for  casting  (fig.  75). 

The  difficulty  of  making  sound  castings  where  the  parts 
are  of  unequal  thickness  also  renders  it  necessary  to  make 
the  thickness  of  the  middle  rib  nearly  equal  to  that  of  the 
flanges. 

20 1.  To  calculate  the  strength  of  a  cast-iron  beam,  the 
sectional  area  of  whose  top  flanges  is  1-6  of  that  of  the  bottom 
ones,  we  must  find  that  of  a  rectangular  beam  of  the  same 
extreme  depth  and  width,  and  deduct  from  it  the  resistance 
of  the  portions  omitted  between  the  top  and  bottom  flanges 

rfig.  15). 

If  we  call  the  whole  width  of  the  bottom  of  the  beam, 
W,  the  sum  of  the  widths  of  the  two  bottom  flanges,  w,  the 
whole  depth  of  the  beam,  D,  and  the  vertical  distance 
between  the  flanges,  d  {on  the  supposition  that  the  top 
flanges  are  of  the  same  widths  as  the  bottom  ones,  and  1-6  of 
their  thickness,  as  shown  by  the  dotted  lines  in  fig.  t8),  the 
distance  between  the  supports,  /,  the  strength  of  the  material, 
Sj  and  if  the  weight  required  to  break  a  beam  when  loosely 
supported  at  the  ends  and  loaded  in  the  middle  be  called  x, 

(W  D'i  —  wd'^)  4  5 

Then  a;  =  , 

I 

and  if  we  take  the  length  in  feet  and  the  other  dimensions 


ART  OF  BUILDING. 


109 


in  inches,  and  call  5  =  560  lbs.,  which  is  not  too  much  for 
the  best  Staffordshire  irons  j  then 

4  5  =  2,240  lbs.  =  1  ton  ;    and  therefore  = 

breaking  weight  in  tons. 

The  value  of  d  in  this  rule  will  be  D  —  t-6  of  the  thickness 
of  the  bottom  flanges,  and  so  long  as  the  sectional  area  of 
the  top  flanges  is  more  than  1-6  of  that  of  the  bottom  ones*, 
the  rule  may  be  applied  to  girders  of  variously  proportioned 
flanges,  as  the  additional  strength  gained  by  increasing  the 
size  of  the  top  flanges  beyond  the  proportion  here  named  is 
very  small  in  proportion  to  the  metal  used,  and,  in  neglecting 
to  take  it  into  account,  we  are  sure  to  err  on  the  safe  side. 

208.  It  must  not  be  supposed,  that  because  increasing  the 
thickness  of  the  top  flanges  does  not  materially  increase  the 
resistance  to  vertical  pressure,  it  is  on  that  account  useless  : 
on  the  contrary,  where  a  beam  is  of  considerable  depth  in 
proportion  to  the  widths  of  the  bottom  flanges,  it  will  often 
be  desirable  to  make  the  top  flanges  more  than  1-6  of  the 
bottom  ones,  in  order  to  prevent  the  girder  from  twisting 
laterally,  and  to  increase  the  resistance  to  any  side  thrust  to 
which  it  may  be  exposed  from  brick  arches  or  otherwise. 

209.  In  practice,  it  is  not  desirable  to  load  iron  girders 
beyond  \  of  their  ultimate  strength,  and  they  should  be 
proved  before  use  by  loading  them  to  this  extent  or  a  little 
more,  but  care  should  be  taken  never  to  let  the  proof  exceed 
1  the  breaking  weight,  as  a  greater  load  than  this  strains 
and  distresses  the  metal,  making  it  permanently  weaker.  The 
ultimate  strength  of  a  girder  of  the  usual  proportions  may 
be  approximately  ascertained  from  its  deflexion  under  proof 

*  It  must  be  remembered  that  in  making  the  top  laanges  narrower  than  the 
bottom  ones  for  convenience  of  casting,  as  the  bulk  of  the  metal  is  brought  nearer 
to  the  neutral  axis  by  so  doing,  the  sectional  area  of  the  top  flanges  must  be  rather 
more  than  1-6  of  that  of  the  bottom  ones,  in  order  to  keep  the  position  of  the  neutral 
axis  the  same  as  in  a  rectangular  beam. 


no 


RUDIMENTS  OF  THE 


on  the  assumption  that  a  load  equal  to  half  the  breaking 
weight  will  cause  a  deflection  of  1-4  8  0th  of  its  length. 

210.  Trussed  Timber  Beams. — Timbers  exposed  to  severe 
strain  require  to  be  trussed  with  iron,  and  this  may  be  done 
in  two  ways  :  1st,  by  inserting  cast-iron  struts,  as  in  fig.  ^6, 
thus  placing  the  whole,  or  nearly  the  whole,  of  the  wood- 


Fig.  76. 


— "'  \ 

"  rf 

work  in  a  state  of  tension  ;  2d,  by  wrought-iron  tension 
rods,  as  in  fig.  7t,  which  take  the  whole  of  the  tension, 


Fig.  77. 


whilst  the  timber  is  thrown  entirely  into  compression.  The 
latter  mode  of  trussing  is  now  very  extensively  used  in 
strengthening  the  carriages  of  traveling  cranes  and  for 
similar  purposes  ;  and,  by  its  use,  a  balk  of  timber  which 
will  barely  support  its  own  weight  safely  without  assistance, 
may  be  made  to  carry  a  load  of  many  tons  without  sensible 
deflection. 

STRENGTH  OF  STORY-POSTS  AND  CAST-IRON  PILLARS. 

211.  When  a  piece  of  timber,  whose  length  is  not  less 
than  8  or  10  times  its  diameter,  is  compressed  in  the  direction 
of  its  length,  as  in  the  case  of  a  wooden  story-post  support- 
ing a  bressummer,  it  will  give  way  if  loaded  beyond  a  certain 
point,  not  by  crushing,  but  by  bending,  and  will  ultimately 
be  destroyed  by  the  cross-strain,  just  as  a  horizontal  beam 
would  be  by  vertical  pressure  applied  at  right  angles  to  the 


ART  OF  BUILDING. 


Ill 


fibres.  The  rules  for  determining  the  dimensions  of  a  piece 
of  timber  to  support  a  given  weight  without  sensible  flexure 
are  very  complicated,  and  are  of  little  practical  value,  as 
they  depend  upon  the  condition  that  the  pressure  is  exactly 
in  the  direction  of  the  axis  of  the  post — a  condition  rarely 
fulfilled  in  practice. 

212.  Wooden  story-posts  have  been  to  a  great  extent 
superseded  by  the  use  of  cast-iron  pillars,  which  possess  great 
strength  with  a  small  sectional  area,  and  are  on  that  account 
particularly  well  adapted  to  situations  where  it  is  of  con- 
sequence to  avoid  obstructing  light,  as  in  shop-fronts. 

In  determining  the  design  of  a  cast-iron  pillar,  whose 
length  is  20  or  30  times  its  diameter,  two  points  have  to  be 
considered  :  1st,  the  liabihty  to  flexure  ;  2d,  the  risk  of  the 
ends  being  crushed  by  the  load  not  acting  in  the  direction 
of  the  axis  of  the  pillar. 

The  resistance  to  flexure  is  greatly 
increased  by  enlarging  the  bearing  surface 
at  the  ends  of  the  pillar,  as  in  fig.  78, 
^  ^  which,  on  the  other  hand,  increases  the 
liability  of  the  ends  to  fracture,  in  the 
event  of  the  load  being  thrown  on  the  side  instead  of  on  the 
centre  of  the  column,  by  any  irregular  settlement  of  the 
building.  The  judicious  architect  will,  therefore  take  a 
mean  course,  swelling  out  the  capitals  and  bases  of  his  cast- 
iron  pillars  enough  to  prevent  their  shafts  from  bending,  but 
at  the  same  time  avoiding  any  thin  flanges  or  projections, 
which  might  be  liable  to  be  broken.  No  theoretical  rule  for 
determining  the  proportions  of  a  cast-iron  pillar  depending 
on  the  weight  to  be  supported  can  be  depended  on  in 
practice.  The  real  measure  of  the  strength  of  a  cast-iron 
story  post  must  be  the  power  of  resisting  any  lateral  force 
which  may  be  brought  against  it  ;  and  as  a  slight  side  blow 
will  suffice  to  fracture  a  pillar  which  is  capable  of  supporting 
a  vertical  pressure  of  very  many  tons,  we  have  only  to  make 


112 


RUDIMENTS  OF  THE 


sure  of  the  lateral  strength,  and  we  are  quite  certain  to  be 
on  the  safe  side  as  regards  any  vertical  pressure  which  it  may 
haij^  to  sustain. 

213.  Besides  the  above  cases  of  transverse  strain,  there 
are  others  arising  from  irregular  settlements,  which  are 
amongst  the  greatest  difficulties  with  which  the  builder  has 
to  contend.  Thus,  to  take  a  familiar  instance,  the  window 
sills  of  a  dwelling-house  are  often  broken  by  the  settlement 
of  the  brick-work  being  greater  in  the  piers  than  under  the 
sills,  from  the  greater  pressure  on  the  mortar  joints  ;  and 
this  will  take  place  with  a  difference  of  settlement  which  can 
scarcely  be  detected,  even  by  careful  measurement*.  We 
need  not  here  enlarge  on  this  subject,  as  we  have  several 
times  in  the  preceding  pages  had  occasion  to  notice  both  the 
causes  of  irregular  settlement,  and  the  precautions  to  be 
taken  for  its  prevention. 

The  strength  of  materials  to  resist  torsion  or  twisting,  as 
in  the  case  of  a  driving  shaft,  is  an  important  consideration 
in  the  construction  of  machinery,  but  is  of  little  consequence 
in  the  erection  of  buildings,  and  therefore  need  not  be  noticed 
in  these  pages. 

*  The  reader  need  scarcely  be  told  that  a  careful  builder  will  always  defer pmnmQ 
up  his  sills  until  some  time  has  been  allowed  for  the  settlement  of  the  brick- work, 
but  this  will  not  always  prevent  ultimate  fracture. 


ART  OF  BUILDING. 


113 


SECTION  lY. 
USE  OF  MATERIALS. 

EXCAVATOR. 

214.  The  digging  required  for  the  foundations  of  common 
buildings  usually  forms  part  of  the  business  of  the  brick- 
layer, and  is  paid  for  at  per  cubic  yard,  according  to  the 
depth  of  the  excavation,  and  the  distance  to  which  the  earth 
has  to  be  wheeled  ;  this  being  estimated  by  the  mn  of  20 
yards. 

In  large  works,  which  require  coffer-dams  and  pumping 
apparatus  to  be  put  down  before  the  ground  can  be  got  out 
for  the  foundations,  the  work  assumes  a  different  character, 
and  is  paid  for  accordingly  ;  the  actual  excavation  being  only 
a  small  item  of  the  total  cost  compared  with  those  of 
dredging,  piling,  puddling,  shoring,  pumping,  &c. 

The  workmen  required  for  the  construction  of  coffer-dams 
and  similar  works  are  laborers  of  a  superior  class,  accustomed 
to  the  management  of  pile-engines  and  tackle,  and  competent 
to  the  execution  of  such  rough  carpenter's  work  as  is  required 
in  timbering  large  excavations. 

BRICKLAYER. 

215.  The  business  of  a  bricklayer  consists  in  the  execution 
of  all  kinds  of  work  in  which  brick  is  the  principal  material ; 
and  in  London  it  always  includes  tiling  and  paving  with 
bricks  or  tiles.  Where  undressed  stone  is  much  used  as  a 
building  material,  the  bricklayer  executes  this  kind  of  work 
also,  and  in  the  country,  the  business  of  the  plasterer  is 
often  united  with  the  above  named  branches. 

8 


114 


RUDIMENTS  OF  THE 


216.  The  tools  of  the  bricklayer  are  the  trowd,  to  take 
up  and  spread  the  mortar,  and  to  cut  bricks  to  the  requiste 
length  :  the  brick  axe,  for  shaping  bricks  to  any  required 
bevel  ;  the  tin  saw,  for  making  incisions  in  bricks  to  be  cut 
with  the  axe,  and  a  rubbing-stone,  on  which  to  rub  the  bricks 
smooth  after  being  roughly  axed  into  shape.  The  jointer  and 
the  jointing-rule  are  used  for  running  the  centres  of  the 
mortar-joints.  The  raker,  for  raking  out  the  mortar  from  the 
joints  of  old  brick-work  previous  to  re-pointing.  The 
hammer,  for  cutting  chases  and  splays.  The  banker  is  a  piece 
of  timber  about  6  feet  long,  raised  on  supports  to  a  con- 
venient height  to  form  a  table  on  which  to  cut  the  bricks  to 
any  required  gauge,  for  which  moulds  and  bevels  are  required. 
The  crowbar,  pick-axe,  and  shovel  are  used  in  digging  out  the 
foundations,  and  the  rammer  in  punning  the  ground  round 
the  footings,  and  in  rendering  the  foundation  firm  where  it  is 
soft  by  beating  or  ramming. 

To  set  out  the  work  and  to  keep  it  true,  the  bricklayer 
uses  the  square,  the  level,  and  the  plumb-rule  ;  for  circular  or 
battering  work  he  uses  templets  and  battering^ules  ;  lines  and 
pins  are  used  to  lay  the  courses  by  ;^and  measuring-rods  to 
take  dimensions.  When  brick-work  has  to  be  carried  up  in 
conjunction  with  stone-work,  the  height  of  each  course  must 
be  marked  on  a  gauge-rod,  that  the  joints  of  each  may 
coincide. 

21 1.  The  bricklayer  is  supplied  with  bricks  and  mortar 
by  a  laborer,  who  carries  them  in  a  hod.  The  laborer  also 
makes  the  mortar,  and  builds  and  strikes  the  scaffolding. 

218.  The  bricklayer^s  scaffold  is  constructed  with  stand- 
ards, ledgers,  and  putlogs.  The  standards  are  fir  poles,  from 
40  to  50  ft.  long,  and  6  or  7  in.  diameter  at  the  butt  ends, 
which  are  fimly  bedded  in  the  ground.  When  one  pole  is 
not  sufficently  long,  two  are  lashed  together,  top  and  butt, 
the  lashings  being  tightened  with  wedges.  The  ledgers  are 
horizontal  poles  placed  parallel  to  the  walls,  and  lashed  to 


ART  OF  BUILDING. 


115 


the  standards  for  the  support  of  the  putlogs.  The  putlogs 
are  cross  pieces,  usually  made  of  birch,  and  about  6  ft.  long, 
one  end  resting  in  the  wall,  the  other  on  a  ledger.  On  the 
putlogs  are  placed  the  scaffold  boards,  which  are  stout  boards 
hooped  at  the  ends  to  prevent  them  from  splitting. 

A  bricklayer  and  his  laborer  will  lay  in  a  single  day  about 
1000  bricks,  or  about  two  cubic  yards. 

The  tools  required  for  tiling  are — the  lathing-hammer,  with 
two  gauge  marks  on  it,  one  at  1,  and  the  other  at  ^\  inches  ; 
the  iron  lathing  staff,  to  clinch  the  nails  ;  the  trowel,  which  is 
longer  and  narrower  than  that  used  for  brick-work  ;  the 
bosse,  for  holding  mortar  and  tiles,  with  an  iron  hook  to  hang 
it  to  the  laths  or  to  a  ladder  ;  and  the  striker,  a  piece  of  lath 
about  10  in.  long,  for  clearing  off  the  superfluous  mortar  at 
the  feet  of  the  tiles. 

219.  Brick-work  is  measured  and  valued  by  the  rod,  or 
by  the  cubic  yard,  the  price  including  the  erection  and  use 
of  scaffolding,  but  not  centering  to  arches,  which  is  an  extra 
charge. 

Bricknogging,  pavings,  and  facings,  by  the  superficial 
yard. 

Digging  and  steining  of  wells  and  cesspools  by  the  foot  in 
depth,  according  to  size,  the  price  increasing  with  the  depth. 

Plain  tiling  and  pantiling  are  valued  per  square  of  100 
feet  superficial. 

MASON. 

220.  The  business  of  the  mason  consists  in  working  the 
stones  to  be  used  in  a  building  to  their  required  shape,  and 
in  setting  them  in  their  places  in  the  work.  Connected  with 
the  trade  of  the  mason  are  those  of  the  Stonecutter,  who  hews 
and  cuts  large  stones  roughly  into  shape  preparatory  to  their 
being  worked  by  the  mason,  and  of  the  Carver,  who  executes 
the  ornamental  portions  of  the  stone-work  of  a  building,  as 
enriched  cornices,  capitals,  &c. 


116 


RUDIMENTS  OF  THE 


221.  Where  the  value  of  stone  is  considerable,  it  is  sent 
from  the  quarry  to  the  building  in  large  blocks,  and  cut  into 
slabs  and  scantlings  of  the  required  size  with  a  stone-mason^s 
saw,  which  differs  from  that  used  in  any  other  trade  in  hav- 
ing no  teeth.  It  is  a  long  thin  plate  of  steel,  slightly  jagged 
on  the  bottom  edge,  and  fixed  in  a  frame  ;  and,  being  drawn 
backwards  and  forwards  in  a  horizontal  position,  cuts  the 
stone  by  its  own  weight.  To  facilitate  the  operation,  a 
heap  of  sharp  sand  is  placed  on  an  inclined  plane  over  the 
stone,  and  water  allowed  to  trickle  through  it,  so  as  to  wash 
the  sand  into  the  saw-cut.  Of  late  years  machinery  worked 
by  steam-power  has  been  used  for  sawing  marble  into  slabs 
to  a  very  great  extent,  and  has  almost  entirely  superseded 
manual  labor  in  this  part  of  the  manufacture  of  chimney- 
pieces. 

Some  freestones  are  so  soft  as  to  be  easily  cut  with  a 
toothed  saw  worked  backwards  and  forwards  by  two  per- 
sons. 

The  harder  kinds  of  stones,  as  granites  and  gritstones,  are 
brought  roughly  into  shape  at  the  quarry,  with  an  axe  or  a 
scappling  hammer,  and  are  then  said  to  be  scajppled. 

222.  The  tools  used  by  the  mason  for  cutting  stone  con- 
sist of  the  mallet  and  chisels  of  various  sizes.  The  mason^s 
mallet  differs  from  that  used  by  any  other  artisan,  being 
similar  to  a  dome  in  contour,  excepting  a  portion  of  the 
broadest  part,  which  is  rather  cylindrical  ;  the  handle  is 
short,  being  only  sufficiently  long  to  enable  it  to  be  firmly 
grasped. 

In  London  the  tools  used  to  work  the  faces  of  stone  are 
the  point,  which  is  the  smallest  description  of  chisel,  being 
never  more  than  a  quarter  of  an  inch  broad  on  the  cutting 
edge  ;  the  inch  tool;  the  boaster,  which  is  2  in.  wide  ;  and 
the  broad  tool,  of  which  the  cutting  edge  is  3|  in.  wide.  The 
tools  used  in  working  mouldings  and  in  carving  are  of  vari- 
ous sizes,  according  to  the  nature  of  the  work. 

Besides  the  above  cutting  tools  the  mason  uses  the 


ART  OF  BUILDING. 


lit 


hanker  or  bench,  on  which  he  places  his  stone  for  conveni- 
ence of  working,  and  straight  edges,  squares,  bevels,  and  tern- 
2)lets,  for  marking  the  shapes  of  the  blocks,  and  for  trying 
the  surfaces  as  the  work  proceeds.  Any  angle  greater  or 
less  than  a  right  angle  is  called  a  bevel  angle,  and  a  hevel 
is  formed  by  nailing  two  straight  edges  together  at  the 
required  angle  ;  a  bevel  square  is  a  square  with  a  shifting 
stock  which  can  be  set  to  any  required  bevel.  A  templet  is 
a  pattern  for  cutting  a  block  to  any  particular  shape  ;  when 
the  work  is  moulded,  the  templet  is  called  a  mould.  Moulds 
are  commonly  made  of  sheet  zinc,  carefully  cut  to  the  profile 
of  the  mouldings  with  shears  and  files. 

For  setting  his  work  in  place  the  mason  uses  the  trowel^ 
liries,  and  pins,  the  square  and  level,  and  plumb,  and  battering 
rules,  for  adjusting  the  faces  of  upright  and  battering  walls. 

223.  The  mason^s  scaffold  is  double,  that  is,  formed  with 
two  rows  of  standards,  so  as  to  be  totally  independent  of  the 
walls  for  support,  as  putlog  holes  are  inadmissible  in 
masonry. 

During  the  last  ten  years  the  construction  of  scaffolds 
with  round  poles  lashed  with  cords  has  been  entirely  super- 
seded in  large  works  by  a  system  of  scaffolding  of  square 
timbers  connected  by  bolts  and  dog  irons. 

The  hoisting  of  the  materials  is  performed  from  these 
scaffolds  by  means  of  a  traveling  crane,  which  consists  of  a 
double  traveling  carriage  running  on  a  tramway  formed  on 
stout  sills  laid  on  the  top  of  two  parallel  rows  of  standards. 
The  crab-winch  is  placed  on  the  upper  carriage,  and,  by 
means  of  the  double  motion  of  the  two  carriages,  can  be 
brought  with  great  ease  and  precision  over  any  part  of  the 
work  lying  between  the  two  rows  of  standards. 

The  facilities  which  are  afforded  by  these  scaffolds  and 
traveling  cranes  for  moving  heavy  weights  over  large  areas, 
have  led  to  their  extensive  adoption,  not  only  in  the  erection 
of  buildings,  but  on  landing  wharfs,  masons  and  ironfound- 


118 


RUDIMENTS  OF  THE 


ers'  yards,  and  similar  situations,  where  a  great  saving  of 
time  and  labor  is  effected  by  their  use. 

224.  The  movable  derrick  crane  is  also  much  used  in 
setting  mason^s  work.  It  consists  of  a  vertical  post  sup- 
ported by  two  timber  backstays,  and  a  long  movable  jib  or 
derrick  hinged  against  the  post  below  the  gearing. 

By  means  of  a  chain  passed  from  a  barrel  over  a  pully  at 
the  top  of  the  post,  the  derrick  can  be  raised  almost  to  a 
vertical,  or  lowered  to  an  almost  horizontal  position,  thus 
enabling  it  to  command  every  part  of  the  area  of  a  circle  of 
a  radius  nearly  equal  to  the  length  of  the  derrick.  This  gives 
it  a  great  advantage  over  the  old  gibbet  crane,  which  only 
commands  a  circle  of  a  fixed  radius,  and  the  use  of  which 
entails  great  loss  of  time  from  its  constantly  requiring  to  be 
shifted  as  the  work  proceeds. 

225.  In  hoisting  blocks  of  stone  they  are  attached  to  the 
tackle  by  means  of  a  simple  contrivance  called  a  lewis,  which 
is  shown  in  fig.  19. 

A  tapering  hole  having  been  cut  in  the  upper  surface  of 
the  stone  to  be  raised,  the  two  side  pieces  of  the  lewis  are 
inserted  and  placed  against  the  sides  of  the  hole  ;  the  centre 
parallel  piece  a  is  then  inserted  and  secured 
in  its  place  by  a  pin  passng  through  all 
three  pieces,  and  the  stone  may  then  be 
safely  hoisted,  as  it  is  impossible  for  the 
lewis  to  draw  out  of  the  hole.  By  means 
of  the  lewis,  in  a  slightly  altered  form  from 
that  here  shown,  stones  can  be  lowered  and 
set  under  water  without  difficulty,  the  lewis 
being  disengaged  by  means  of  a  line  attach- 
ed to  the  parallel  piece  ;  the  removal  of  which  allows  the 
others  to  be  drawn  out  of  the  mortice. 

226.  In  stone-cutting,  the  workman  forms  as  many  plane 
faces  as  may  be  necessary  for  bringing  the  stone  into  the 


Fig.  79. 


ART  OF  BUILDING. 


119 


required  shape,  with  the  least  waste  of  material  and  labor, 
and  on  the  plane  surfaces  so  formed  applies  the  moulds  to 
which  the  stone  is  to  be  worked 

To  form  a  plane  surface,  the  mason  first  knocks  off  the 
superfluous  stone  along  one  edge  of  the  block,  slH     b  ( fig. 

80),  until  it  coincides  with  a 
^^S*  straight  edge  throughout  its 


whole  length  ;  this  is  called 
a  chisel  draught.  Another 
chisel  draught  is  then  made 
along  one  of  the  adjacent 


edges  as  Z>,  c,  and  the  ends  of 
the  two  are  connected  by  ano- 
ther draught,  as  a  c;  a  fourth  draught  is  then  sunk  across 
the  last,  as  5,  d,  which  gives  another  angle  point  d,  in  the 
same  plane  with  a  b,  and  c,  by  which  the  draughts  d  a  and 
a  c  can  be  formed  ;  and  the  stone  is  then  knocked  off  be- 
tween the  outside  draughts  until  a  straight  edge  coincides 
with  the  surface  in  every  part. 

To  form  cylindrical  or  moulded  surfaces  curved  in  one 
direction  only,  the  workman  sinks  two  parallel  draughts  at 

the  opposite  end  of  the  stone  to 

Fig.  81. 

be  worked,  until  they  coincide 
with  a  mould  cut  to  the  required 
shape,  and  afterwards  works  off 
the  stone  between  these  draughts, 
by  a  straight  edge  applied  at 
right  angles  to  them  (fig.  81). 
The  formation  of  conical  or 
spherical  surfaces  is  much  less  simple,  and  require  a  know- 
ledge of  the  scientific  operations  of  stone-cutting,  a  description 
of  which  would  be  unsuited  to  the  elemetary  character  of 
these  pages. 

22 The  finely-grained  stones  are  usually  brought  to  a 
smooth  face,  and  rubbed  with  sand  to  produce  a  perfectly 
even  surface. 


120 


RUDIMENTS  OF  THE 


.  In  working  soft  stones,  the  surface  is  brought  to  a  smooth 
face  with  the  drag,  which  is  a  plate  of  steel,  indented  on  the 
edge  like  the  teeth  of  a  saw,  to  take  off  the  marks  of  the 
tools  employed  in  shaping  it. 

The  harder  and  more  coarsely  grained  stones  are  generally 
tooled,  that  is,  the  marks  of  the  chisel  are  left  on  their  face. 
If  the  furrows  left  by  the  chisel  are  disposed  in  regular 
order,  the  work  is  said  to  be  fair-tooled,  but  if  otherwise,  it 
may  be  random-tooled  or  chiseled  or  boasted  or  pointed.  If 
the  stones  project  beyond  the  joints,  the  work  is  said  to  be 
rusticated. 

Granite  and  gritstone  are  chiefly  worked  with  the  scap- 
pling  hammer.  In  massive  erections,  where  the  stones  are 
large,  and  a  bold  effect  is  required,  the  fronts  of  the  blocks 
are  left  quite  rough,  as  they  come  out  of  the  quarry,  and  the 
work  is  then  said  to  be  quarry  pitched. 

Many  technical  terms  are  used  by  quarrymen  and  others 
engaged  in  working  stone  ;  but  they  need  not  be  inserted 
here,  as  they  are  mostly  confined  to  particular  localities  be- 
yond which  they  are  little  known,  or  perhaps  bear  a  different 
signification. 

228.  When  the  mason  requires  to  give  to  the  joints  of 
his  work  greater  security  than  is  afforded  by  the  weight  of 
the  stone  and  the  adhesion  of  the  mortar,  he  makes  use  of 
joggles,  dowels,  and  cramps. 

Stones  are  said  to  be  joggled  together  when  a  projection 
is  worked  out  on  one  stone  to  fit  into  a  corresponding  hole 
or  groove  in  the  other  {see  fig.  82).    But  this 
Fig.  82.     occasions  great  labor  and  waste  of  stone,  and 
^        dowel-joggles  are  chiefly  made  use  of,  which  are 
hard  pieces  of  stone,  cut  to  the  required  size, 
and  let  into  corresponding  mortices  in  the  two  stones  to  be 
joined  together. 

Dowels  are  pins  of  wood  or  metal  used  to  secure  the 
joints  of  stone-work  in  exposed  situations,  as  copings,  pin- 


ART  OF  BUILDING. 


121 


nacles,  &c.  The  best  material  is  copper  ;  but  tlie  expense 
of  this  metal  causes  it  to  be  seldom  used.  If  iron  be  made 
use  of,  it  should  be  thoroughly  thinned  to  prevent  oxidation, 
or  it  will,  sooner  or  later,  burst  and  split  the  work  it  is  in- 
tended to  protect. 

Dowels  are  often  secured  in  their  places  with  lead  poured  iu 
from  above,  through  a  small  channel  cut  in  the  side  of  the 
joint  for  that  purpose  ;  but  a  good  workman  will  eschew 
lead,  which  too  often  finds  his  way  into  bad  work,  and  will 
prefer  trusting  to  very  close  and  workmanlike  joints,  care- 
fully fitted  dowels,  and  fine  mortar  ;  dowels  should  be  made 
tapering  at  one  end,  which  ensures  a  better  fit,  and  renders 
the  setting  of  the  stone  more  easy  for  the  workman. 

L'on  cramps  are  used  as  fastenings  on  the  tops  of  copings, 
and  in  similar  situations  ;  but  they  are  not  to  be  recom- 
mended, as  they  are  very  unsightly,  and,  if  they  once  become 
exposed  to  the  action  of  the  atmosphere,  are  powerfully  de- 
structive agents.  Cast  iron  is,  however,  less  objectionable 
than  wrought  iron  for  this  purpose. 

229  In  measuring  mason^s  work,  the  cubic  content  of  the 
stone  is  taken  as  it  comes  to  the  hanker^  without  deduction 
for  subsequent  waste. 

If  the  scantlings  are  large,  an  extra  price  is  allowed  for 
hoisting. 

The  labor  in  working  the  stone  is  charged  by  the  super- 
ficial foot,  according  to  the  kind  of  work,  as  plain  work,  sunk 
work,  moulded  work,  &c 

Pavings  landings,  &c.,  and  all  stones  less  than  three  in. 
thick,  are  charged  by  the  superficial  foot. 

Copings,  curbs,  window  sills,  &c.,  are  charged  per  lineal 
foot. 

Cramps,  dowels,  mortice  holes,  &c.,  are  always  charged 
separately. 

The  remuneration  of  a  stone-carver  is  dependent  on  his 
talent,  and  the  kind  of  work  he  is  engaged  upon. 


122 


RUDIMENTS  OF  THE 


CARPENTER. 

230.  The  business  of  the  carpenter  consists  in  framing 
timbers  together,  for  the  construction  of  roofs,  partitions, 
floors,  &c. 

231.  The  capenter's  principal  tools  are  the  axe,  the  adze, 
the  saw,  and  the  chisel,  to  which  may  be  added  the  chalk, 
line,  plumb-rule,  level,  and  square.  The  work  of  the  carpen- 
ter does  not  require  the  use  of  the  plane,  which  is  one  of 
the  principal  tools  of  the  joiner,  and  this  forms  the  principal 
distinction  between  these  trades,  the  carpenter  being  engaged 
in  the  rough  frame-work,  and  the  joiner  on  the  finishings  and 
decorations  of  buildings. 

232.  The  principles  of  framing  have  been  already  fully 
described  in  the  1st  section  of  this  work,  and  we  shall,  there- 
fore, confine  our  remarks  on  the  operations  of  the  carpenter 
to  a  description  of  the  principal  joints  made  use  of  in  framing. 

Timbers  that  have  to  be  joined  in  the  direction  of  their 
length,  are  scarfed,  as  shown  in  fig.  83  ;  the  double  wedges. 
a  a,  serve  to  bring  the  timbers  homej  when  they  are  secured, 


Fig.  83. 


either  by  bolts,  as  shown  at  5  5  or  by  straps,  as  at  c  c,  the 
latter  being  the  most  perfect  and  the  most  expensive  fas- 
tening. 

Fig.  84  shows  the  manner  of  connecting  the  foot  of  a 
principal  rafter  with  a  tie-beam.    The  bolt  here  shown  keeps 


ART  OF  BUILDING. 


123 


Fig,  84. 


the  rafter  in  its  place,  and  prevents  it  from  slipping  away 
from  the  abutment  cut  for  it,  which,  by  throwing  the  thrust 

on  the  tenon,  would  probably  split 


The  king-post  should  be  cut  somewhat  short,  to  give  the 
power  of  screwing  up  the  framing  after  the  timber  has  be- 
come fully  seasoned.  The  tie-beam  may  be  suspended  from 
the  king-post,  either  by  a  bolt,  as  shown,  or  by  a  strap  passed 
round  the  tie-beam  and  secured  by  iron  wedges  or  cotters, 
passing  through  a  hole  in  the  king-post  ;  this  last  is  the 
more  perfect,  but  at  the  same  time  the  more  expensive  of  the 
two  methods. 

Fig.  85  also  shows  the  manner  in  which  the  feet  of  the 
struts  butt  upon  the  king-post.  They  are  slightly  tenoned 
to  keep  them  in  their  places.  The  ends  of  a  strut  should  be 
cut  off  as  nearly  square  as  possible,  otherwise,  when  the  tini-^ 
ber  shrinks,  which  it  always  does,  more  or  less,  the  thrust  is 
thrown  upon  the  edge  only,  which  spUts  ox  crushes  ui^der  the 
pressure,  and  causes  settlement. 

This  is  shown  out  by  the  dotted  lines  on  the  right-hand 
side  of  the  cut.    The  dotted  lines  on  the  opposite  side  of  the 


Fig.  85. 


it.  The  end  of  the  rafter  should 
be  cut  with  a  square  butt,  so 
that  the  shrinkage  of  the  tim- 
ber will  not  lead  to  any  settle- 
ment. 


The  connection  of  the  foot  of 
a  king-post  with  the  tie-beam  to 
be  suspended  from  it  is  shown  in 
fig.  85. 


124 


RUDIMENTS  OF  THE 


figure  show  a  similar  effect,  produced  by  the  shrinking  of  the 
king-post,  for  which  there  is  no  preventive  but  making  it 
of  oak,  or  some  other  hard  wood.  The  same  observations 
apply  to  the  connections  of  the  principal  rafters  with  the  top 
of  the  king-post,  which  are  managed  in  a  precisely  similar 
manner. 

In  figures  86,  8^,  and  88,  are  shown  different  methods 


Fig.  86.  Fig.  87. 


In  figures  44,  45,  46,  and  47,  are  shown  the  modes  of 
framing  the  ends  of  binding  joists  into  girders,  and  of  con- 
necting the  ceiling  joists  with  the  binders  ;  and  as  these  have 
been  already  described  under  the  head  of  Floors,"  it  is 
unnecessary  here  to  say  anything  further  on  the  subject. 


ART  OF  BUILDING.  125 

As  a  general  rule,  all  timbers  should  be  notched  down  to 
those  on  which  they  rest,  so  as  to  prevent  their  being  moved 
either  lengthways  or  sideways.  Where  an  upright  post  has 
to  be  fixed  between  two  horizontal  sills,  as  in  the  case  of  the 
uprights  of  a  common  framed  partition,  it  is  simply  tenoned 
into  them,  and  the  tenons  secured  with  oak  pins  driven 
through  the  cheeks  of  the  mortice. 

233.  The  carpenter  requires  considerable  bodily  strength 
for  the  handling  of  the  timbers  on  which  he  has  to  work  ; 
he  should  have  a  knowledge  of  mechanics,  that  he  may  under- 
stand the  nature  of  the  strains  and  thrusts  to  which  his  work 
is  exposed,  and  the  best  method  of  preventing  or  resisting 
them  ;  and  he  should  have  such  a  knowledge  of  working 
drawings  as  will  enable  him,  from  the  sketches  of  the 
architect,  to  set  out  the  lines  for  every  description  of  center- 
ing and  framing  that  may  be  entrusted  to  him  for  execution. 

234.  In  measuring  carpenters^  work  the  tenons  are  included 
in  tne  length  of  the  timber  :  this  is  not  the  case  in  joiners' 
work,  in  which  they  are  allowed  for  in  the  price. 

The  labor  in  framing,  roofs,  partitions,  floors,  &c.,  is  either 
valued  at  per  square  of  100  superficial  feet,  and  the  timber 
charged  for  separately,  or  the  timber  is  charged  as  "  fixed  in 
place,"  the  price  varying  according  to  the  labor  ^n  it.  as 
^'  cube  fir  in  bond,"  cube  fir  framed,"  ''cube  fir  wrougno 
and  framed,"  &c.  For  shoring  |  of  the  value  of  the  timber 
is  allowed  for  use  and  waste. 

JOINER. 

235.  The  work  of  the  joiner  consists  in  framing  and 
joining  together  the  wooden  finishings  and  decorations  of 
buildings,  both  internal  and  external,  such  as  floors,  stair- 
cases, framed-partitions,  skirtings,  solid  door  and  window 
frames,  hollow  or  cased  window  frames,  sashes  and  shutters, 
doors,  columns  and  entablatures,  chimney-pieces,  &c.,  &c. 


126  RUDIMENTS  OF  THE 

The  joiner^s  work  requires  much  greater  accuracy  and 
finish  than  that  of  the  carpenter,  and  differs  materially  from 
it  in  being  brought  to  a  smooth  surface  with  the  plane 
wherever  exposed  to  view,  whilst  in  carpenters'  work  the 
timber  is  left  rough  as  it  comes  from  the  saw. 

236.  The  joiner  uses  a  great  variety  of  tools  ;  the  principal 
cutting  tools  are  sawSj  jplanes^  and  chisels. 

Of  saws  there  are  many  varieties,  distinguished  from  each 
other  by  their  shape  and  by  the  size  of  the  teeth. 

The  ripper  has  8  teeth  in  3  inches  ;  the  half-rijp;per  3  teeth 
to  the  inch  ;  the  hand  saw  15  teeth  in  4  inches  ;  the  ]^and 
saw  6  teeth  to  the  inch. 

The  tenon  saw,  used  for  cutting  tenons,  has  about  8  teeth 
to  the  inch,  and  is  strengthened  at  the  back  by  a  thick  piece 
of  iron,  to  keep  the  blade  from  buckling.  The  sash  saw  is 
similar  to  the  tenon  saw,  but  is  backed  with  brass  instead  of 
iron,  and  has  13  teeth  to  the  inch.  The  dovetail  saw  is  still 
smaller,  and  has  15  teeth  to  the  inch. 

Besides  the  above,  other  saws  are  used  for  particular  pur- 
poses, as'the  compass  saw,  for  cutting  circular  work,  and  the 
,vcy-aoLt  daw,  for  cutting  out  small  holes.  The  carcase  saw  is 
a  large  kind  of  dovetail  saw,  having  about  11  teeth  to  an 
inch. 

231.  Planes  are  also  of  many  kinds ;  those  called  lenck 
planes — as  the  jack  plane,  the  trying  plane,  the  long  plane,  the 
jointer,  and  the  smoothing  plam,  are  used  for  bringing  the 
stuff  to  a  plane  surface.  The  jack  plane  is  about  18  inches 
long,  and  is  used  for  the  roughest  work.  The  trying  plane 
is  about  22  in.  long,  and  used  after  the  jack  plane  for  trying 
up,  that  is,  taking  off  shavings  the  whole  length  of  the  stuff ; 
whilst  in  using  the  jack  plane  the  workman  stops  at  every 
arm's-length.  The  long  plane  is  2  ft.  3  in.  long,  and  is  used 
when  a  piece  of  stuff  is  to  be  tried  up  very  straight.  The 


ART  OF  BUILDING. 


jointer  is  2  ft.  6  in.  long,  and  is  used  for  trying  up  or  shooting 
the  joints,  in  the  same  way  as  the  trying  plane  is  used  for 
trying  up  the  face  of  the  stuff.  The  smoothing  plam  is  small, 
being  only  t|  in.  long,  and  is  used  on  almost  all  occasions 
for  cleaning  off  finished  work. 

Rebate  planes  are  used  for  sinking  rebates  {see  fig.  89), 
and  vary  in  their  size  and  shape  according  to  their  respective 
.  uses.  Rebate  planes  difi*er  from  bench  planes 
Fig.  89.  having  no  handle  rising  out  of  the  stock, 

and  in  discharging  their  shavings  at  the  side. 
Amongst  the  rebate  planes  may  be  mentioned 
the  ffwving  fillister  and  the  sask  fillister ,  the 
uses  of  which  will  be  better  understood  by 
inspection  than  from  any  description. 

Moulding  planes  are  used  for  sticking  mouldings,  as  the 
operation  of  forming  mouldings  with  the  plane  is  called. 
When  mouldhigs  are  worked  out  with  chisels  instead  of  with 
planes,  they  are  said  to  be  worked  by  hand.  Of  the  class 
of  moulding  planes,  although  kept  separate  in  the  tool  chest, 
are  hollows  and  rounds  of  various  sizes. 

There  are  other  kinds  of  planes  besides  the  above  ;  as  the 
plough,  for  sinking  a  groove  to  receive  a  projecting  tongue  ; 
the  bead  plam,  for  sticking  beads  ;  the  snipe  bill,  for  forming 
quirks  ;  the  compass  plam  and  the  forkstaff  plane,  for  forming 
concave  and  convex  cylindrical  surfaces.  The  shape  and  use 
of  these  and  many  other  tools  used  by  the  joiner  will  be 
better  understood  by  a  visit  to  the  joiner's  shop  than  by  any 
verbal  description, 

238.  Chisels  are  also  varied  in  their  form  and  use.  Some 
are  used  merely  with  the  pressure  of  the  hand,  as  the  paring 
chisel ;  others,  by  the  aid  of  the  mallet,  as  the  socket  chisd^^ 
for  cutting  away  superfluous  stuff ;  and  the  nwrtice  chisel^  for 
•cutting  niortices.    The  gouge  is  a  curved  chisel 


*  Named  from  the  iroB  forming  a  socket  to  receiya  ja  wjocdexi  Jjajodj^. 


128 


RUDIMENTS  OF  THE 


239.  The  joiner  uses  a  great  variety  of  boring  tools,  as 
the  hrad-awlj  gimlet,  and  stock  and  lit.  The  last  form  but 
one  tool,  the  dock  being  the  handle,  to  the  bottom  of  which 
may  be  fitted  a  variety  of  steel  bits  of  different  bores  and 
shapes,  for  boring  and  widening  out  holes  in  wood  and  metal, 
as  countersinks,  rimers^  and  tajper  shdl  bits, 

240.  The  screw  driver,  jpincers,  hammer,  malld,  hatchet,  and 
adze,  are  too  well  known  to  need  description. 

The  gauge  is  used  for  drawing  lines  on  a  piece  of  stuff 
parallel  to  one  of  its  edges. 

The  hench  is  one  of  the  most  important  of  the  joiner^s  im- 
plements. It  is  furnished  with  a  vertical  sideboard,  perfo- 
rated with  diagonal  ranges  of  holes,  which  receive  the 
hemck  pin  on  which  to  rest  the  lower  end  of  a  piece  of  stuff 
to  be  planed^  whilst  the  upper  end  is  firmly  clamped  by  the 
le7ich  screvj. 

The  mit7X  box  is  used  for  cutting  a  piece  of  stuff  to  a  mire 
or  angle  of  45  degrees  with  one  of  its  sides. 

The  joiner  uses  for  setting  out  and  fixing  his  work — the 
straight  edge,  the  square,  the  bevel  or  square  with  a  shifting 
blade,  the  mitre  squai^,  the  level,  and  the  plumb  rule. 

In  addition  to  the  tools  and  implements  above  enumerated, 
the  execution  of  particular  kinds  of  work  require  other  arti« 
cles,  as  cylinders,  templets,  cramps,,  &c.> 
Fig.  90.         the  description  of  which  would  unneces- 
^  sarily  extend  the  limits  of  tliis  volume. 

Qjf  /     ^      The  principal  operations  of  the  joiner 
are  sawing,  planing,  dovetailing,  mortis- 
ing,  and  scribing. 
I  The  manner  of  f arming  a  dovefaH  is 

I  shown  in  fig  90.    The  projecting  part,  a, 

is  called  the        and  the  hole  to  receive  it  is  called  thd 


ART  OF  BUILDING. 


129 


Fig.  91. 


Mortising  is  shown  in  fig.  91  ;  the  projecting  piece  is 
called  the  tenon^  and  the  hole 
formed  to  receive  it  the  mortice. 
The  tenon  is  sometimes  pinned  in 
its  place  with  oak  pins  driven 
through  the  cheeks  of  the  mor- 
tice ;  but  in  forming  doors,  shut- 
ters, &c.,  the  tenon  is  secured 
with  tapering  wedges  driven  into 
the  mortice,  which  is  cut  slightly 
wider  at  the  top  than  at  the  bottom,  the  adhesion  of  the 
glue  with  which  the  wedges  are  first  rubbed  over,  making  it 
impossible  for  the  tenon  afterwards  to  draw  out  of  its  place. 

241  Joints  in  the  length  of  the  stuff  "may  be  either  square, 
as  at     fig.  92,  or  rebated,  as  at  b,  or  grooved  and  tongued, 


oc-  l>  c 

as  at  c,  or  grooved  on  each  edge  and  a  tongue  let  in,  as  at  d, 

242.  Scribing  is  the  drawing  on  a  piece  of  stuff  the  exact 
profile  of  some  irregular  surface  to  which  it  is  to  be  made  to 
fit :  this  is  done  with  a  pair  of  compasses,  one  leg  of  which  is 
made  to  travel  the  irregular  surface,  the  other  to  describe  a 
line  parallel  thereto  along  the  edge  of  the  stuff  to  be  cut. 

243.  In  the  execution  of  circular,  or,  as  it  is  termed,  sweep 
work,  there  are  four  different  methods  by  which  the  stuff  can 
be  brought  to  the  required  curve  : — 

1st.  It  may  be  steamed  and  bent  into  shape. 

2nd.  It  may  be  glued  up  in  thicknesses,  as  shown  in  fig. 


Fig.  93. 


93,  which  must,  when  thoroughly 
dry,  be  planed  true,  and,  if  not  to 
to  be  painted,  covered  with  a  thin 
veneer  bent  round  it. 

3rd.    It  may  be  formed  in  thin 
thicknesses,  as  shown  in  fig.  94, 
9 


130 


RUDIMENTS  OF  THE 


bent  round  and  glued  up  in  a  mould.  This  may  be  consider- 
ed the  most  perfect  of  all  the  methods  in  use. 

Fig.  94.  Fig.  95. 

Lastly.  It  may  be  formed  by  sawing  a  number  of  notches 
on  one  side,  as  shown  in  fig.  95,  by  which  means  it  becomes 
easily  bent  in  that  direction,  but  the  curve  produced  by  this 
means  is  very  irregular,  and  it  is  an  inferior  mode  of  execu- 
tion compared  to  the  others. 

When  a  number  of  boards  are  secured  together  by  cross- 
pieces  or  ledges  nailed  or  screwed  at  the  back,  the  work 
is  said  to  be  ledged  {see  fig.  96). 
Fig.  96      Fig.  97.     Ledged  work  is  used  for  common 
purposes,  as*  cellar   doors,  outside 
shutters,  &c. 

Framed  icork  (fig.  97),  consists  of 
styles  and  rails  mortised  and  tenoned 
together,  and  filled  in  with  pannels, 
the  edges  of  which  fit  in  grooves  cut 
in  the  styles  and  rails. 
Work  is  said  to  be  damped  when  it  is  prevented  from 
warping  or  splitting  by  a  rail  at  each  end,  as  in  fig.  98  ;  if 
the  ends  of  the  rail  are  cut  ofi*,  as  shown 
Fig  98.  at  a,  it  is  said  to  be  mitre  clamped. 

There  are  two  ways  of  laying  floors 
practised  by  joiners.  In  laying  what  is 
called  a  straigfd  joint  floor,  from  the 
joints  between  the  boards  running  in  an 
unbroken  line  from  wall  to  wall,  each 
board  is  laid  down  and  nailed  in  succes- 
sion, being  first  forced  firmly  against  the  one  last  laid  with 
a  flooring  cramp. 


LEDCE 


ART  OF  BUILDING. 


131 


Folding  floors  are  laid  by  nailing  down  first  every  fifth 
board  rather  closer  together  than  the  united  widths  of  four 
boards,  and  forcing  the  intermediate  ones  into  the  space 
left  for  them  by  jumping  over  them  ;  this  method  of  laying 
floors  is  resorted  to  when  the  stuff  is  imperfectly  seasoned 
and  is  expected  to  shrink,  but  it  should  never  be  allowed  in 
good  work. 

The  narrow^er  the  stuff  with  which  a  floor  is  laid  the  less 
will  the  joints  open,  on  account  of  the  shrinkage  being  dis- 
tributed over  a  greater  number  of  joints. 

The  floor  boards  may  be  nailed  at  their  edges  and  grooved 
and  tongued  or  dowelled,  if  it  be  wished  to  make  a  very 
perfect  floor.  Dowelling  is  far  superior  to  grooving  and 
tonguing,  because  the  cutting  away  the  stuff  to  receive  the 
tongue  greatly  weakens  the  edges  of  the  joint,  which  are 
apt  to  curl. 

244.  Glue  is  an  article  of  great  importance  to  the  joiner  ; 
the  strength  of  his  work  depending  much  upon  its  adhesive 
properties. 

The  best  glue  is  made  from  the  skins  of  animals  ;  that 
from  the  sinewy  or  horny  parts  being  of  inferior  quality. 
The  strength  of  the  glue  increases  with  the  age  of  the  ani- 
mals from  which  the  skins  are  taken. 

Joiners'  work  is  measured  by  the  superficial  foot,  accord- 
ing to  its  description. 

Floors  by  the  square  of  100  superficial  feet 

Handrails,  small  mouldings,  water-trunks,  and  similar 
articles,  per  lineal  foot. 

Cantilevers,  trusses,  cut-brackets,  scrolls  to  handrails,  &e., 
are  valued  per  piece. 

Ironmongery  is  charged  for  with  the  work  to  which  it  is 
attached  ;  the  joiner  being  allowed  20  per  cent,  profit  upon 
the  prime  cost. 

The  principal  articles  of  ironmongery  used  in  a  building 
consist  of  nails  and  screws^  sash  j^ullies,  boltSj  hinges^  locks^ 


132 


RXTDIMENTS  OF  TIIE 


latches  J  and  sash  shutter  furmture^  besides  a  great  variety  of 
miscellaneous  articles,  which  we  have  not  space  to  enumerate. 

Of  the  different  kinds  of  hinges  may  be  mentioned  hook  and 
tye,  hinges^  for  gates,  coach-house  doors,  &c. ;  hutts  and  hack" 
JlajpSy  for  doors  and  shutters  ;  crosss-garnets  of  H  form^  which 
are  used  for  hanging  ledged  doors,  and  other  inferior  work  ; 
|—  and  H —  hinges,  whose  name  is  derived  from  their  shape  ; 
and  parliament  hinges. 

Besides  these  are  used  rising  hutts^  for  hanging  doors  to 
rise  over  a  carpet,  or  other  impediment  ;  projecting  butts, 
used  when  some  projection  has  to  be  cleared,  and  spring 
hinges  and  siving  centres  for  self-shutting  doors. 

The  variety  of  locks  now  manufactured  is  almost  infinite. 
We  may  mention  the  stock  lock,  cased  in  wood,  for  common 
work.  Rim  locks  which  have  a  metal  case  or  rim,  and  are 
attached  to  one  side  of  a  door  :  they  should  not  be  used 
when  a  door  has  sufficient  thickness  to  allow  of  a  mortice 
lock,  as  they  often  catch  the  dresses  of  persons  passing 
through  the  doorway.  Mortice  locks,  as  the  name  implies, 
are  those  which  are  morticed  to  the  thickness  of  a  door. 

The  handles  and  escutcheons  are  called  the  furniture  of  a 
lock,  and  are  made  of  a  great  variety  of  materials,  as  brass, 
bronze,  ebony,  ivory,  glass,  &c. 

Of  latches,  there  are  the  common  thumb  latch,  the  bow 
latch,  with  brass  knobs,  the  brass  pulpit  latch  and  the  mortice 
latch. 

The  sawyer  is  to  the  carpenter  and  joiner  what  the  stone- 
cutter is  to  the  mason. 

The  fit  saw  is  a  large  two-handed  saw  fixed  in  a  frame, 
and  moved  up  and  down  in  a  vertical  direction,  by  two  men, 
called  the  top-man  and  the  pit-man;  the  first  of  whom  stands 
on  the  timber  that  is  to  be  cut,  the  other  at  the  bottom  of 
the  saw  pit.  The  timber  is  lined  out  with  a  chalk  line  on  its 
upper  surface,  and  the  accuracy  of  the  work  depends  mainly 
on  the  top-man  keeping  the  saw  to  the  hne,  whence  the  pro- 


ART  OF  BUILDING. 


133 


verbial  expression  to]^  sawer^  meaning  one  who  directs  any 
undertaking. 

In  sawing  np  deals  and  battens  into  thicknesses  for  the 
joiner's  use,  the  parallehsm  of  the  cuts  is  of  the  utmost  im- 
portance, as  the  operation  of  taking  out  of  windings  a  piece 
of  uneven  stuff,  causes  a  considerable  waste  of  material,  and 
much  loss  of  time. 

Circular  saws,  moved  by  steam-power,  are  now  much  used 
in  large  establishments,  timber  yards,  &c.,  and  effect  a  great 
saving  of  labor  over  the  use  of  the  pit  saw,  where  the  tim- 
bers to  be  cut  are  not  too  heavy  to  be  easily  handled.  The 
saw  is  mounted  in  the  middle  of  a  stout  bench,  furnished 
with  guides,  by  means  of  which  the  stuff  to  be  cut  is  kept  in 
the  required  direction,  whilst  it  is  pushed  against  the  saw, 
which  is  the  whole  of  the  manual  labor  required  in  the  ope- 
ration. 

SLATER. 

245.  The  business  of  the  slater  consists  chiefly  in  covering 
the  roofs  of  houses  with  slates,  but  it  has  of  late  years  being 
very  much  extended  by  the  general  introduction  of  sawn 
slate,  as  a  material  for  shelves,  cisterns,  baths,  chimney- 
pieces,  and  even  for  ornamental  purposes. 

We  propose  here  to  describe  only  those  operations  of  the 
slater  which  have  reference  to  the  covering  of  roofs. 

246.  Besides  the  tools  which  are  in  use  among  other  arti- 
ficers, the  slater  uses  one  peculiar  to  his  trade  called  the^<2a;, 
which  is  a  kind  of  hatchet,  with  a  sharp  point  at  the  back. 
It  is  used  for  trimming  slates,  and  making  the  holes  by 
which  they  are  nailed  in  their  places. 

24 T.  Slates  are  laid  either  on  boarding  or  on  narrow  bat- 
tens, from  2  to  3  inches  wide,  the  latter  being  the  more 
common  method,  on  account  of  its  being  less  expensive  than 
the  other. 

The  nails  used  should  be  either  copper  or  zinc;  iron  nails, 


134 


RUDIMENTS  OF  THE 


though  sometimes  used,  being  objectionable,  from  their  liar 
bility  to  rust. 

Every  slate  should  be  fastened  with  two  nails,  except  in 
the  most  inferior  work. 

The  upper  surface  of  a  slate  is  called  its  lack,  the  under 
surface  the  bed  the  lower  edge  the  tail,  the  upper  edge  the 
head.  The  part  of  each  course  of  slates  exposed  to  view  is 
called  the  margin  of  the  course,  and  the  width  of  the  margin 
is  called  the  gauge. 

The  bond  or  laj^  is  the  distance  which  the  lower  edge  of 
any  course  overlaps  the  slates  of  the  second  course  below, 
measuring  from  the  nail-hole. 

In  preparing  slates  for  use,  the  sides  and  bottom  edges 
are  trimmed,  and  the  nail-holes  punched  as  near  the  head  as 
can  be  done,  without  risk  of  breaking  the  slate,  and  at  a 
uniform  distance  from  the  tail. 

The  lap  having  been  decided  on,  the  guage  will  be  equal 
to  half  the  distance  from  the  tail  to  the  nail-hole,  less  the  lap. 
Thus  a  countess  slate,  measuring  19  in.  from  tail  to  nail,  if 

19  in.— 3  in. 

laid  with  a  3  in.  lap,  would  show  a  margin  of  — 


8  in.  (fefigs.  99.  100.) 
Fig.  99. 


Fig.  100. 


1  . 

bo 

-4f- — 

The  battens  are  of  course  nailed  on  the  rafters  at  the 
gauge  to  which  the  slate  will  work.  If  the  slates  are  of 
different  lengths,  they  must  be  sorted  into  sizes,  and  gauged 
accordingly,  the  smallest  sizes  being  placed  nearest  the  ridge. 
The  lap  should  not  be  less  than  2,  and  need  not  exceed  3  in. 


ART  OF  BUILDING. 


135 


It  is  essential  to  the  soundness  as  well  as  the  appearance 
of  slaters^  work,  that  the  slates  should  all  be  of  the  same 
width,  and  the  edges  perfectly  true. 

The  Welsh  slates  are  considered  the  best,  and  are  of  a 
light  sky  blue  color.  The  Westmoreland  slates  are  of  a  dull 
greenish  hue. 

248.  Slaters'  work  is  measured  by  the  square  of  100  su- 
perficial feet,  allowances  being  made  for  the  trouble  of  cut- 
ting the  slates  at  the  hips,  eaves,  round  chimneys,  &c. 

Slabs  for  cisterns,  baths,  shelves,  and  other  sawn  work, 
are  charged  per  superficial  foot,  according  to  the  thickness 
of  the  slab  and  the  labor  bestowed  on  the  work. 

Rubbed  edges,  grooves,  &c.,  are  charged  per  lineal  foot. 


Table  of  Sizes  of  Roofing  Slates. 


Desckifhon. 

Size. 

Average 
gauge  in 

No.  of 

squares 
1200  will 
cover. 

Weight 
per  1200 

No.  re- 
quired 
to  cover 

No.  of 

nails 
required 

Length. 

Breadth. 

inches  . 

in  tons. 

one 
square. 

to  one 
square. 

Doubles  .  . 
Ladies  .  .  . 
Countesses 
Duchesses 

ft. 
1 
1 
1 

2 

in. 
1 

4 
8 
0 

ft.  in. 

0  6 
0  8 

0  10 

1  0 

7 
9 

10)4 

2 

7 
10 

K 

2 
3 

480 
280 
176 
127 

480 
280 
352 
254 

Imperials  . 
Kags  and 

Queens 
Westmere- 

lands,  of 

2 
3 

6 
0 

2  0 
2  0 

1  a  ton  will  cover  2^  to  2)^  squares. 

various 

sizes. 

Inch  slab  per  superficial  weighs  14  lbs. 


PLASTERER. 

249.  The  work  of  the  plasterer  consists  in  covering  the 
brickwork  and  naked  timber  walls,  ceilings,  and  partitions 


136 


RUDIMENTS  OF  THE 


with  plaster,  to  prepare  them  for  painting,  papering,  or  dis* 
tempering  ;  and  in  forming  cornices,  and  such  decorative 
portions  of  the  finishings  of  buildings  as  may  be  required  to 
be  executed  in  plaster  or  cement. 

250.  The  plasterer  uses  a  variety  of  tools,  of  which  the 
following  are  the  principal  ones  : — 

The  drag  is  a  three-pronged  rake,  used  to  mix  the  hair 
with  the  mortar  in  preparing  coarse  stuff. 

The  hawk  is  a  small  square  board  for  holding  stuff  on, 
with  a  short  handle  on  the  under  side. 

Trowels  are  of  two  kinds,  the  laying  and  smoothing  tool, 
with  which  the  first  and  the  last  coats  are  laid,  and  the 
gauging  trowel,  used  for  gauging  fine  stuff  for  cornices,  &c.  ; 
these  are  made  of  various  sizes,  from  3  to  7  in,  long. 

Of  floats,  which  are  used  in  floating,  there  are  three  kinds, 
viz.,  the  Derby,  which  is  a  rule  of  such  a  length  as  to  require 
two  men  to  use  it  ;  the  hand  float,  which  is  used  in  finishing 
stucco  ;  and  the  quirk  fl,oat,  which  is  used  in  floating 
angles. 

Moulds,  for  running  cornices,  are  made  of  sheet  copper, 
cut  to  the  profile  of  the  moulding  to  be  formed,  and  fixed  in 
a  wooden  frame. 

Stopping  and  picking  out  tools  are  made  of  steel,  7  or  8  in. 
long,  and  of  various  sizes.  They  are  used  for  modeling, 
and  for  finishing  mitres  and  returns  to  cornices. 

251.  Materials. — Coarse  stuff,  or  lime  and  hair,  as  it  is 
usually  called,  is  similar  to  common  mortar,  with  the  addition 
of  hair  from  the  tanners^  yard,  which  is  thoroughly  mixed 
with  the  mortar  by  means  of  the  drag. 

Fin£  stuff  is  made  of  pure  lime,  slaked  with  a  small 
quantity  of  water,  after  which,  sufficient  water  is  added  to 
bring  it  to  the  consistence  of  cream. 

It  is  then  allowed  to  settle,  and  the  superfluous  water 
being  poured  off,  it  is  left  in  a  binn  or  tub  to  remain  in  a 
semifluid  state  until  the  evaporation  of  the  water  has  brought 


ART  OF  BUILDING. 


13t 


it  to  a  proper  thickness'  for  use.  In  using  fine  stuff  for 
setting  ceilings,  a  small  portion  of  white  hair  is  mixed 
with  it. 

Stucco  is  made  with  fine  stuff,  and  clean-washed  sand.  This 
is  used  for  finishing  work  intended  to  be  painted. 

Gauged  stuff  is  formed  of  fine  stuff  mixed  with  plaster  of 
Paris,  the  proportion  of  plaster  varying  according  to  the 
rapidity  with  which  the  work  is  required  to  set.  Gauged 
stuff  is  used  for  running  cornices  and  mouldings. 

Enrichments,  such  as  pateras,  centre  flowers  for  ceilings, 
&c.,  are  first  modeled  in  clay,  and  afterwards  cast  of  plaster 
of  Paris  in  wax  or  plaster  moulds.  Papier  mache  ornaments 
also  are  much  used,  and  have  the  advantage  of  being  very 
light,  and  being  easily  and  securely  fixed  with  screws. 

The  variety  of  compositions  and  cements  made  use  of  by 
the  plasterer  is  very  great.  Poman  cement,  Portland  cement, 
and  lias  cement,  are  the  principal  ones  used  for  coating  build- 
ings externally.  Martinis  and  Keene^s  cements  are  well 
adapted  for  all  internal  plastering  where  sharpness,  hardness, 
and  delicate  finish  are  required. 

252.  Operations  of  Plastering. — When  brick-work  is 
plastered,  the  first  coat  is  called  rendering. 

In  plastering  ceilings  and  partitions,  the  first  operation  is 
lathing.  This  is  done  with  single,  one  and  a  half,  or  douUe 
laths  ;  these  names  denoting  their  respective  thicknesses. 
Laths  are  either  of  oak  or  fir  ;  if  the  former,  wrought-iron 
nails  are  used,  but  cast-iron  may  be  employed  with  the 
latter.  The  thickest  laths  are  used  for  ceilings,  as  the  strain 
on  the  laths  is  greater  in  a  horizontal  than  in  an  upright 
position. 

Pricking  up  is  the  first  coat  of  plastering  of  course  stuff 
upon  laths  ;  when  completed,  it  is  well  scratched  over  with 
the  end  of  a  lath,  to  form  a  key  for  the  next  coat. 

Laid  work  consists  of  a  simple  coat  of  coarse  stuff  over  a 
wall  or  ceiling. 


138 


RUDIMENTS  OF  THE 


Two-coat  work  is  a  cheap  description  of  plastering,  in 
which  the  first  coat  is  only  roughed  over  with  a  broom,  and 
afterwards  set  with  fine  stuff,  or  with  gauged  stuff  in  the 
better  descriptions  of  work. 

The  laying  on  of  the  second  coat  of  plastering  is  called 
floating  J  from  its  being  floated^  or  brought  to  a  plane  surface 
with  the  float. 

The  operation  of  floating  is  performed  by  surrounding  the 
surface  to  be  floated  with  narrow  strips  of  plastering,  called 
screeds,  brought  perfectly  upright,  or  level,  as  the  case  may 
be,  with  the  level  or  plumb-rule  ;  thus,  in  preparing  for 
floating  a  ceiling,  nails  are  driven  in  at  the  angles,  and  along 
the  sides,  about  10  ft.  apart,  and  carefully  adjusted  to  a 
horizontal  plane,  by  means  of  the  level.  Other  nails  are 
then  adjusted  exactly  opposite  to  the  first,  at  a  distance  of 
7  or  8  in.  from  them.  The  space  between  each  pair  of  nails 
is  filled  up  with  coarse  stuff,  and  leveled  with  a  hand  float  ; 
this  operation  forms  what  are  called  dots.  When  the  dots 
are  sufficiently  dry,  the  spaces  between  the  dots  are  filled  up 
flush  with  coarse  stuff,  and  floated  perfectly  true  with  a  float- 
ing rule ;  this  operation  forms  a  screed,  and  is  continued  until 
the  ceiling  is  surrounded  by  one  continuous  screed,  perfectly 
level  throughout.  Other  screeds  are  then  formed,  to  divide 
the  work  into  bays  about  8  ft.  wide,  which  are  successively 
filled  up  flush,  and  floated  level  with  the  screeds. 

The  screeds  for  floating  walls  are  formed  in  exactly  the 
same  manner,  except  that  they  are  adjusted  with  the  plumb- 
rule  instead  of  the  level. 

After  the  work  has  been  brought  to  an  even  surface  with 
the  floating  rule,  it  is  gone  over  with  the  hand  float,  and  a 
little  soft  stuff,  to  make  good  any  deficiencies  that  may 
appear. 

The  operation  of  forming  screeds  and  floating  work,  which 
is  not  either  vertical  or  horizontal,  as  a  plaster  floor  laid 
with  a  fall,  is  analogous  to  that  of  taking  the  face  of  a  stone 
out  of  winding  with  chisel-drafts  and  straight  edges  in  stone- 


ART  OF  BTHLDING. 


139 


cutting  ;  the  principle  being  in  each  case  to  find  three  points 
in  the  same  plane,  from  which  to  extend  operations  over  the 
whole  surface. 

Setting. — When*  the  floating  is  about  half  dry,  the  setting 
or  finishing  coat  of  fine  stuff  is  laid  on  with  the  smoothing 
trowel,  which  is  alternately  wetted  with  a  brush  and  worked 
over  with  the  smoothing  tool,  until  a  fine  surface  is  obtained. 

Stucco  is  laid  on  with  the  largest  trowel,  and  v/orked  over 
with  the  hand  float,  the  work  being  alternately  sprinkled 
with  water,  and  floated  until  it  becomes  hard  and  compact, 
after  which  it  is  finished  by  rubbing  it  over  with  a  dry  stock 
brush. 

The  water  has  the  effect  of  hardening  the  face  of  the 
stucco,  so  that,  after  repeated  sprinklings  and  trowelings,  it 
becomes  very  hard,  and  smooth  as  glass. 

253.  The  above  remarks  may  be  briefly  summed  up  as 
follows.  The  commonest  kind  of  work  consists  of  only  one 
coat,  and  is  called  rendering,  on  brick-work,  and  laying,  if 
on  laths.  If  a  second  coat  be  added,  it  becomes  two-coat 
work,  as  render-set,  or  lath  lay  and  set.  When  the  work  is 
floated,  it  becomes  three-coat  work,  and  is  render,  float,  and 
set,  for  brick-work,  and  lath,  lay,  float,  and  set,  for  ceilings 
and  partitions  ;  ceilings  being  set  with  fine  stuff,  with  a  little 
white  hair,  and  walls  intened  for  paper  with  fine  stuff  and 
sand  ;  stucco  is  used  where  the  work  is  to  be  painted. 

Rovgh  stucco  is  a  mode  of  finishing  staircases,  passages, 
&c.,  in  imitation  of  stone.  It  is  mixed  with  a  large  propor- 
tion of  sand,  and  that  of  a  coarser  quality  than  troweled 
stucco,  and  is  not  smoothed,  but  left  rough  from  the  hand 
float,  which  is  covered  with  a  piece  of  felt,  to  raise  the  grit 
of  the  sand,  to  give  the  work  the  appearance  of  stone. 

Rough  cast  is  a  mode  of  finishing  outside  work,  by  dash- 
ing over  the  second  coat  of  plastering,  whilst  quite  wet,  a 
layer  of  rough-cast,  composed  of  well-washed  gravel,  mixed 
up  with  pure  lime  and  water,  till  the  whole  is  in  a  semifluid 
state. 


140 


RUDIMENTS  OF  THE 


Pugging  is  lining  the  spaces  between  floor  joists  with 
coarse  stuff,  to  prevent  the  passage  of  sound,  or  between  two 
stones,  and  is  done  on  laths  or  rough  boarding. 

In  the  midland  districts  of  England,  refeds  are  much  used 
instead  of  laths,  not  only  for  ceihngs  and  partitions,  but  for 
floors,  which  are  formed  with  a  thick  layer  of  coarse  gauged 
stuff  upon  reeds.  Floors  of  this  kind  are  extensively  used 
about  Nottingham ;  and,  from  the  security  against  fire 
afforded  by  the  absence  of  wooden  floors,  Nottingham  houses 
are  proverbially  fire-proof. 

254.  Plasterer^s  work  is  measured  by  the  superficial  yard  ; 
cornices  by  the  superficial  foot ;  enrichments  to  cornices  by 
the  lineal  fool ;  and  centre  flowers  and  other  decorations  at 
per  piece. 

MEMORANDA. 

Lathing. — One  bundle  of  laths  and  384  nails  will  cover  5 
yards. 

Rendering. — 18 1|  yards  require  1|  hundred  of  lime,  2 
double  loads  of  sand,  and  5  bushels  of  hair. 

Floating  requires  more  labor,  but  only  half  as  much 
material  as  rendering. 

Setting. — 3t5  yards  require  1\  hundred  of  lime,  and  5 
bushels  of  hair. 

Render  set. — 100  yards  require  1|  hundred  of  lime,  1 
double  load  of  sand,  and  4  bushels  of  hair.  Plasterer, 
laborer,  and  boy,  3  days  each. 

Lath,  lay,  and  set. — 130  yards  of  lath,  lay,  and  set,  require 
1  load  of  laths,  10,000  nails,  2i  hundred  of  lime,  1|  double 
load  of  sand,  and  1  bushels  of  hair.  Plasterer,  laborer,  and 
boy,  6  days  each. 

SMITH  AND  IRONFOUNDER. 

255.  The  smith  furnishes  the  various  articles  of  wrought, 
iron  work  used  in  a  building ;  as  pileshoes,  straps,  screw- 


ART  OF  BUILDING. 


141 


bolts,  dog-irons,  cliimney  bars,  gratings,  wrought-iron  rail- 
ing, and  wrouglit-iron  balustrades  for  staircases.  Wrought 
iron  was  formerly  much  used  for  many  purposes,  for  which 
cast  iron  is  now  almost  exclusively  employed  ;  the  improve- 
ments effected  in  casting  during  the  present  century  having 
made  a  great  alteration  in  this  respect. 

The  operations  of  the  ironfounder  have  been  described  in 
Section  II.  of  this  volume,  and  therefore  we  have  only  here 
to  enumerate  some  of  the  principal  articles  which  are 
furnished  by  him. 

Besides  cast-iron  columns,  girders,  and  similar  articles 
which  are  cast  to  order,  the  founder  supplies  a  great  variety 
of  articles  which  are  kept  in  store  for  immediate  use  ;  as 
cast-iron  gratings,  balconies,  rain-water  pipes  and  guttering, 
air  traps,  coal  plates,  stoves,  stable  fittings,  iron  sashes,  &c. 

Both  wrought  and  cast-iron  work  are  paid  for  by  weight, 
except  small  articles  kept  in  store  for  immediate  use,  which 
are  valued  per  piece. 

lbs. 

One  cubic  foot  of  cast  iron  weighs  about  450 
Ditto  wrought  ,,  475 

Ditto  closely  hammered  485 

256.  The  Coppersmith  provides  and  lays  sheets  of  copper 
for  covering  roofs  ;  copper  gutters,  and  rainwater  pipes  ; 
washing  and  brewing  coppers  ;  copper  cramps  and  dowels 
for  stonemasons'  work  ;  and  all  other  copper  work  in  a 
building  ;  but  the  cost  of  the  material  in  which  he  works 
prevents  its  general  use  ;  and  the  washing  copper  is  fre- 
quently the  only  part  of  a  building  which  requires  the  aid 
of  this  artificer.  Sheet  copper  is  paid  for  by  the  superficial 
foot,  according  to  weight,  and  pipes  and  gutters  per  lineal 
foot  ;  copper  in  dowels,  bolts,  &c.,  at  per  pound. 

257.  Warming  apparatus,  steam  and  gas  fittings,  and  simi- 
lar kinds  of  work,  are  put  up  by  the  mechanical  engineer, 
who  also  manufactures  a  great  variety  of  articles,  which  are 


RUDIMENTS  OF  TfiE 


purchased  in  parts,  and  put  together  and  fixed  by  the 
plumber,  as  pumps,  taps,  water-closet  apparatus,  &c. 

258.  The  hell-hanger  provides  and  hangs  the  bells  required 
for  communicating  between  the  different  parts  of  a  building, 
and  connects  them  with  their  fulls ^  or  handles,  by  means  of 
cranks  and  wires. 

The  action  of  the  pull  upon  the  bell  should  be  as  direct, 
and  effected  with  as  few  cranks  as  possible  ;  and  the  cranks 
and  wires  should  be  concealed  from  view,  both  to  protect 
them  from  injury,  and  on  account  of  their  unsightly  appear- 
ance. 

In  all  superior  work,  the  wires  are  conducted  along  con- 
cealed tubes,  fixed  to*the  walls  before  the  plasterer's  work 
is  commenced.  The  simplest  way  of  arranging  the  wires  is 
to  carry  them  up  in  separate  tubes  to  the  roof,  where  they 
may  all  be  conducted  to  one  point,  and  brought  down  a 
chase  in  the  walls  to  the  part  of  the  basement  where  the 
bells  are  hung,  By  this  means  very  few  cranks  are  required, 
and  a  broken  wire  can  be  replaced  at  any  time  without 
trouble. 

259.  Bell-hangers'  work  is  paid  for  by  the  number  of  bells 
hung  ;  the  price  being  determined  by  the  manner  in  which 
the  work  is  executed.  The  furniture  to  the  pulls  is  charged 
in  addition,  at  per  piece. 

PLUMBER. 

260.  The  work  of  the  plumber  chiefly  consists  in  laying 
sheet  lead  on  roofs,  lining  cisterns,  laying  on  water  to  the 
different  parts  of  a  building,  and  fixing  up  pumps  and  water 
closets. 

261.  The  plumber  uses  but  few  tools,  and  those  are  of  a 
simple  character  ;  the  greater  number  of  them  being  similar 
to  those  used  by  other  artificers,  as  hammer mallets ^  planes, 
chisds,  gouges  J  files  j  &c.    The  principal  tool  peculiar  to  the 


ART  OF  BUILDING. 


148 


trade  of  the  plumber  is  the  hat^  which  is  made  of  beech, 
about  18  in.  long,  and  is  used  for  dressing  and  flattening 
.sheet  lead.  For  soldering  also  the  plumber  uses  iron  ladles, 
of  various  sizes,  for  melting  solder,  and  grozing  irons,  for 
smoothing  down  the  joints. 

262.  The  sheet  lead  used  by  the  plumber  is  either  cast  or 
milled,  the  former  being  generally  cast  by  the  plumber  him- 
self out  of  old  lead  taken  in  exchange  ;  whilst  the  latter, 
which  is  cast  lead,  flattened  out  between  rollers  in  a  flatting 
mill,  is  purchased  from  the  manufacturer.  Sheet  lead  is  de- 
scribed according  to  the  weight  per  superficial  foot,  as  5-lb. 
lead,  6-lb.  lead,  &c. 

Lead  pipes,  if  of  large  diameter,  are  made  of  sheet  lead, 
dressed  round  a  wooden  core,  and  soldered  up. 

Smaller  pipes  are  cast  in  short  lengths,  of  a  thickness 
three  or  four  four  times  that  of  the  intended  pipe,  and  either 
drawn  or  rolled  out  to  the  proper  thickness. 

Soft  Solder  is  used  for  uniting  the  joints  of  lead-work. 
It  is  made  of  equal  parts  of  lead  and  tin,  and  is  purchased 
of  the  manufacturer  by  the  plumber,  at  a  price  per  lb.,  ac- 
cording to  the  state  of  the  market. 

263.  Laying  of  Sheet  Lead.— In  order  to  secure  lead- 
work  from  the  injurious  elfects  of  contraction  and  expansion, 
when  exposed  to  the  heat  of  the  sun,  the  plumber  is  careful 
not  to  confine  the  metal  by  soldered  joints  or  otherwise. 
All  sheet  lead  should  be  laid  to  a  sufficient  current ^  to  keep 
it  dry  ;  a  fall  of  1  in.  in  10  ft.  is  sufficient  for  this  purpose, 
if  the  boarding  on  which  the  lead  is  laid  be  perfectly  even. 
Joints  in  the  direction  of  the  current  are  made  by  dressing 
the  edges  of  the  lead  over  a  wooden  roll,  as  shown  in  fig. 
101. 

Joints  in  the  length  of  the  current  are  made  with  drij)Sj 
as  shown  on  the  left-  hand-side  of  fig.  102. 


RUDIMENTS  OF  THE 


Fig,  101.  Fig,  102. 

Flashings  are  pieces  of  lead  turmd  down  over  the  ed^es  of 
the  other  lead-work,  which  is  turned  up  against  a  wall,  as 
shown  on  the  right-hand  side  of  fig.  lOT,  and  serve  to  keep 
the  wet  from  finding  its  way  between  the  wall  and  the  lead. 
The  most  secure  way  of  fixing  them  is  to  build  them  into 
the  joints  of  the  brickwork,  but  the  common  method  is  to 
insert  them  about  an  inch  into  the  mortar  joint,  and  to  secure 
them  with  wall  hooks  and  cement.    {See  fig.  102.) 

264.  A  very  important  part  of  the  business  of  the  plumber 
consists  in  fitting  up  cisterns,  pumps,  and  water-closet  appa- 
ratus, and  in  laying  the  different  services  and  wastes  con- 
nected with  the  same. 

265  Plumber's  work  is  paid  for  by  the  cwt.,  milled  lead 
being  rather  more  expensive  than  cast. 

Lead  pipes  are  charged  per  foot  lineal,  according  to  size. 

Pumps  and  water-closet  apparatus  are  charged  at  so  much 
each,  according  to  description  ;  as  also,  basins,  air  traps, 
washers  and  plugs,  spindle  valves,  stop-cocks,  ball-cocks,  &c. 

Table  of  the  Weight  of  Lead  Pipes,  per  yard. 

Bore.  lb.  oz, 

1  inch   33 

i  „    5  7 

1  „    8  0 

U  „    11  0 

H  „    14  0 

2  „   21  0 

ZINC  WORKER. 

266.  The  use  of  sheet  lead  has  been  to  a  certain  extent 
superseded  by  the  use  of  sheet  zinc,  which,  from  its  cheap- 
ness and  lightness,  is  very  extensively  used  for  almost  all 


ART  OF  BUILDING. 


145 


purposes  to  wliicli  sheet  lead  is  applied.  It  is,  however,  a 
very  inferior  material,  and  not  to  be  depended  upon.  The 
laying  of  it  is  generally  executed  by  the  plumber  ;  but  the 
working  of  zinc,  and  manufacturing  of  it  into  gutters,  rain- 
water pipes,  chimney  cowls,  and  other  articles,  is  practised 
as  a  distinct  busine^ss, 

GLAZIER. 

26Y.  The  business  of  the  glazier  consists  in  cutting  glass, 
and  fixing  it  into  lead-work,  or  sashes.  The  former  is  the 
oldest  description  of  glazing,  and  is  still  used,  not  only  for 
cottage  windows,  and  inferior  work,  but  for  church  windows, 
and  glazing  with  stained  glass,  which  is  cut  into  pieces  of 
the  required  size,  and  set  in  a  leaden  framework  j  this  kind 
of  glazing  is  called  f  rdworL 

268,  Glazing  in  sashs  is  of  comparatively  modern  intro- 
duction. The  sash-bars  are  formed  with  a  rebate  on  the  out- 
side, for  the  reception  of  the  glass,  which  is  cut  into  the 
rebates,  and  firmly  bedded  and  back]puttied  to  keep  it  into  its 
place.  Large  squares  are  also  s^rigged^  or  secured  with 
small  brads  driven  into  the  sash  bars, 

269.  Glazing  hi  lead-work  is  fixed  in  leaden  rods,  called 
canm,  prepared  for  the  use  of  the  glazier  by  being  passed 
through  a  glazier's  vice,  in  which  they  receive  the  grooves 
for  the  insertion  of  the  glass.  The  sides  or  cheeks  of  the 
grooves  are  sufficiently  soft  to  allow  of  their  being  turned 
down  to  admit  the  glass,  and  again  raised  up  and  firmly 
pressed  against  it  after  its  insertion. 

For  common  lead-work,  the  bars  are  soldered  together,  so 
as  to  form  squares  or  diamonds.  In  fretwork,  the  bars,  in- 
stead of  being  used  straight,  are  bent  round  to  the  shapes 
of  the  different  pieces  of  glass  forming  the  device — lead- 
work  is  strengthened  by  being  attached  to  saddle  bars  of 
iron,  by  leaden  bands  soldered  to  the  lead-work,  and  twisted 
round  the  iron. 

10 


146 


RUDIMENTS  OF  THE 


Putty  is  made  of  pounded  whiting,  beaten  up  with  linseed 
oil  into  a  tough,  tenaeeous  cement. 

2 to.  The  principal  tool  of  the  glazier  is  the  diamoTid, 
which  is  used  for  cutting  glass.  This  tool  consists  of  an 
unpoKshed  diamond  fixed  in  lead,  and  fastened  to  a  handle 
of  hard  wood. 

The  glazier  uses  a  hacking  out  knife^  for  cutting  out  old 
putty  from  broken  squares  ;  and  the  stojyping  knife,  for  laying 
and  smoothing  the  putty  when  stojpjping-in  glass  into-  sashes. 

For  setting  glass  into  lead-work  the  setting  knife  i^  used. 

Besides  the  above,  the  glazier  requires  a  square  and 
straight  edges,  a  rule  and  a  pair  of  compasses,  for  dividing 
the  tables  of  glass  to  the  required  sizes. 

Also  a  hammer  and  brushes,  for  sprigging  large  squares, 
and  cleaning  off  the  work. 

The  glazier^s  vice  has  already  been  mentioned  ;  the  latter- 
kin  is  a  pointed  piece  of  hard  wood,  with  which  the  grooves 
of  the  cames  are  cleared  out  and  widened  for  receiving  the 
glass.  '  • 

271.  Cleaning  windows  is  an  important  branch  of  the 
glazier\s  business  in  most  large  towns  ;  the  glazier  taking 
upon  himself  the  cost  of  repairing  all  glass  broken  in 
cleaning. 

272.  Glaziers'  work  is  valued  by  the  superficial  foot,  the 
price  increasing  with  the  size  of  the  squares.  Irregular 
panes  are  taken  of  the  extreme  dimensions  each  way. 

Crown  glass  is  blown  in  circular  tables  from  3  ft.  6  in.  to  5 
ft.  diameter,  and  is  sold  in  crates,  the  number  of  tables  in  a 
crate  varying  according  to  the  quality  of  the  glass. 
A  crate  contains  12  tables  of  best  quality. 
„         „       15     „        second  do. 
„         „       18     „        third  do. 
Plate  glass  is  cast  on  large  plates  on  horizontal  tables, 
and  afterwards  polished. 


ART  OF  BUILDING. 


14T 


The  manufacture  of  sheet  or  spread  glass,  which  was  for- 
merly considered  a  very  inferior  article,  has  of  late  years 
been  much  improved  ;  much  is  now  sold,  after  being  polished, 
under  the  name  of  Patent  Plate. 

PAINTER,   PAPERHANGER,  AND  DECORATOR. 

2 13.  The  business  of  the  house-painter  consists  in  cover- 
ing, with  a  preparation  of  white  lead  and  oil,  such  portions 
of  the  joiner's,  smith's,  and  plasterer's  work  as  require  to  be 
protected  from  the  action  of  the  atmosphere.  Decorative 
painting  is  a  higl^er  branch,  requiring  a  knowledge  of  the 
harmony  of  colors,  and  more  or  less  of  artistic  skill,  accord- 
ing to  the  nature  of  the  work  to  be  executed.  The  intro- 
duction of  fresco  painting  into  this  country  as  a  mode  of  in- 
ternal decoration  has  led  to  the  employment  of  some  of  the 
first  artists  of  the  day  in  the  embellishment  of  the  mansions 
of  the  wealthy  ;  and  the  example  thus  set  will,  no  doubt, 
be  extensively  followed. 

274.  The  principal  materials  used  by  the  painter  Sire  while 
leadj  which  forms  the  basis  of  almost  all  the  colors  used  in 
house-painting  ;  linseed  oil*  and  spirits  of  turjpentine,  used  for 
mixing  and  diluting  the  colors  ;  and  dryers,  as  litharge, 
sugar  of  lead,  and  white  vitriol,  which  are  mixed  with  the 
colors  to  facilitate  their  drying  Putty,  made  of  whiting 
and  linseed  oil,  is  used  for  stopping  or  filling  up  nail  holes, 
and  other  vacuities,  in  order  to  bring  the  work  to  a  smooth 
face. 

2t5.  The  painter's  tools  are  few  and  simple  ;  they  consist 
of  the  grinding  stone  and  viuller,  for  grinding  colors  ;  earthen 
pots  J  to  hold  colors  ;  cans,  for  oil  and  turps  ;  a  pallet  hnife^ 
and  brushes  of  various  sizes  and  descriptions. 

2T6.  In  painting  wood-work,  the  first  operation  consists 
in  killing  the  knots,  from  which  the  turpentine  would  other- 
wise exude  and  spoil  the  work.    To  effect  this,  the  knots  are 


148 


RUDIMENTS  OF  THE 


covered  with  fresh  slaked  lime,  which  dries  up  and  burns  out 
the  turpentine.  When  this  has  been  on  twenty-four  hours, 
it  is  scraped  off,  and  the  knots  painted  over  with  a  mixture 
of  red  and  white  lead,  mixed  with  glue  size.  After  this  they 
are  gone  over  a  second  time  with  red  and  white  lead,  mixed 
with  linseed  oil.  When  dry,  they  must  be  rubbed  perfectly 
smooth  with  pumice  stone,  and  the  work  is  ready  to  receive 
the  priming  coat.  This  is  composed  of  red  and  white  lead, 
well  diluted  with  hnseed  oil.  The  nail  holes  and  other  im- 
perfections are  then  stopped  with  putty,  and  the  succeeding 
coats  are  laid  on,  the  work  being  rubbed  down  between  each 
coat,  to  bring  it  to  an  even  surface.  The  first  coat  after  the 
priming  is  mixed  with  linseed  oil  and  a  little  turpentine.  The 
second  coat  with  equal  quantities  of  linseed  oil  and  turpen- 
tine. In  laying  on  the  second  coat,  where  the  work  is  not  to 
be  finished  white,  an  approach  must  be  made  to  the  required 
color.  The  third  coat  is  usually  the  last,  and  is  made  with  a 
base  of  white  lead,  mixed  with  the  requisite  color,  and 
diluted  with  one-third  of  linseed  oil  to  two-thirds  of  turpen- 
tine. 

Painting  on  stucco,  and  all  other  work  in  which  the  sur- 
face is  required  to  be  without  gloss,  has  an  additional  coat 
mixed  with  turpentine  only,  which,  from  its  drying  of  one 
uniform  flat  tint,  is  called  a  flatting  coat. 

If  the  knots  show  through  the  second  coat,  they  must  be 
carefully  covered  with  silver  leaf. 

Work  finished  as  above  described  would  be  technically 
specified  as  knotted,  primed,  painted  three  oils,  and  flatted. 

Flatting  is  almost  indispensable  in  all  delicate  interior 
work,  but  it  is  not  suited  to  outside  work,  as  it  will  not  bear 
exposure  to  the  weather. 

2^^.  Painting  on  stucco  is  primed  with  boiled  linseed  oil, 
and  should  then  receive  at  least  three  coats  of  white  lead 
and  oil,  and  be  finished  with  a  flat  tint.  The  great  secret 
p£,  success  in  painting  stucco  is  that  the  surface  should  be 


ART  OF  BUILDING. 


149 


perfectly  dry  ;  and,  as  this  can  hardly  be  the  case  in  less 
than  two  years  after  the  erection  of  a  building,  it  will  always 
be  advisable  to  finish  new  work  in  distemper,  which  can  be 
washed  off  whenever  the  walls  are  sufficiently  dry  to  receive 
the  permanent  decorations 

278.  Graining  is  the  imitation  of  the  grain  of  various 
kinds  of  woods,  by  means  of  graining  tools,  and,  when  well 
executed,  and  properly  varnished,  has  a  handsome  appear- 
ance, and  lasts  many  years.  The  term  graining  is  also 
applied  to  the  imitation  of  marbles. 

279.  Clear  coling  (from  claire  colle,  i.  e.  transparent  size, 
Fr.),  is  a  substitution  of  size  for  oil,  in  the  preparation  of 
the  priming  coat.  It  is  much  -resorted  to  by  painters  on 
account  of  the  ease  with  which  a  good  face  can  be  put  on 
the  work  with  fewer  coats  than  when  oil  is  used  ;  but  it  will 
not  stand  damp,  which  causes  it  to  scale  off,  and  it  should 
never  be  used  except  in  repainting  old  work,  which  is  greasy 
or  smoky,  and  cannot  be  made  to  look  well  by  any  other 
means. 

280.  Distemjpering  is  a  kind  of  painting  in  which  whiting 
is  used  as  the  basis  of  the  colors,  the  liquid  medium  being 
size  ;  it  is  much  used  for  ceilings  and  walls,  and  always  will 
require  two,  and  sometimes  three  coats,  to  give  it  a  uniform 
appearance, 

281.  Painters'  work  is  valued  per  superficial  yard,  accord- 
ing to  the  number  of  coats,  and  the  description  of  work,  as 
common  colors,  fancy  colors,  party  colors,  &c. 

Where  work  is  cut  in  on  both  edges,  it  is  taken  by  the 
lineal  foot.  In  measuring  railings,  the  two  sides  are  measured 
as  flat  work.  Sash  frames  are  valued  per  piece,  and  sashes 
at  per  dozen  squares. 

282.  The  manufacture  of  scagliola,  or  imitation  marble, 
is  a  branch  of  the  decorator's  business,  which  is  carried  to 
very  great  perfection. 


150 


RUDIMENTS  OF  THE 


Scagliola  is  made  of  plaster  of  taris  and  different  earthy 
colors,  which  are  mixed  in  a  trough  in  a  moist  state,  and 
blended  together  until  the  required  effect  is  produced,  when 
the  composition  is  taken  from  the  trough,  laid  on  the  plaster 
ground,  and  well  worked  into  it  with  a  wooden  beater,  and 
a  small  gauging  trowel.  When  quite  hard,  it  is  smoothed, 
scraped,  and  polished,  until  it  assumes  the  appearance  of 
marble. 

Scagliola  is  valued  at  per  superficial  foot,  according  to  the 
description  of  marble  imitated,  and  the  execution  of  the 
work. 

283.  Gilding  is  executed  with  leaf  gold,  which  is  furnish- 
ed by  the  gold-beater  in  books  of  25  leaves,  each  leaf 
measuring  3i  in.  by  3  in.  The  parts  to  be  gilded  are  first 
prepared  with  a  coat  of  gold  size,  which  is  made  of  Oxford 
ochre  and  fat  oil. 

284.  The  operations  of  the  paper-hanger  are  too  simple  to 
require  description. 

A  piece  of  paper  is  12  yards  long,  and  is  20  ins.  wide, 
when  hung,  and  covers  6  ft.  superficial  ;  hence  the  number 
of  superficial  feet  that  have  to  be  covered,  divided  by  60, 
will  give  the  number  of  pieces  required. 

Paper-hangers'  work  is  valued  at  per  piece,  according  to 
the  value  of  the  paper. 

The  trades  of  the  plumber,  glazier,  painter,  paper-hanger, 
and  decorator  are  often  carried  on  by  the  same  person. 

DRAINAGE. 

285.  The  principal  classes  of  buildings  as  subjects  for 
water  supply  and  drainage,  are — 1.  Dwellings  ;  2.  Manufac- 
tories ;  and  3.  Public  buildings. 

There  is  no  certain  date  upon  which  to  calculate  the  extent 
of  the  arrangement  to  be  provided  for  the  joint  purposes  of 
supplying  water  and  discharging  sewerage.    In  England  the 


ART  OF  BUILDING. 


151 


calculations  of  water  companies  are  usually  based  upon  the 
rental  paid  for  each  house  as  an  index  to  the  consumption  of 
water  within  it,  and  in  this  way  they  recognize  an  almost 
infinite  number  of  classes. 

286.  It  is  estimated  that  20  gallons  of  water  is  the 
average  daily  quantity  for  each  inhabitant  of  a  town,  and 
that  this  quantity  is  sufficient  to  allow  also  for  an  ordinary 
proportion  of  manufacturing  operations,  for  the  supply  of 
public  buildings,  and  for  the  extinction  of  fires.  It  is 
estimated  that  a  bulk  of  water  measuring  6  feet  in  length  by 
1|  feet  in  width  and  1  ft.  in  depth,  will  suffice  for  the  ablution 
of  one  person  in  the  baths.  This  quantity  will  equal  9  cubic 
feet,  or  about  54  gallons. 

28  iT.  Sewers  and  drains  were  formerly  devised  with  the 
single  object  of  making  them  large  enough^  by  which  it  was 
supposed  that  their  full  efficiency  was  secured.  But  sluggish- 
ness of  the  action  is  now  recognized  as  the  certain  conse- 
quence of  excess  equally  as  of  deficiency  of  declination.  A 
small  stream  of  liquid  matter  extended  over  a  wide  surface, 
and  reduced  in  depth  in  proportion  to  this  width,  suffers 
retardation  from  the  want  of  declivity  in  the  current.  Hence 
a  drain  which  is  disproportionally  large  in  comparison  to  the 
amount  of  drainage  -is  concentrated  within  a  more  limited 
channel,  a  greater  rapidity  is  produced,  and  every  addition 
to  the  contents  of  the  aids  by  the  full  force  of  its  gravity  in 
propelling  the  entire  quantity  forward  to  the  point  of  dis- 
charge. 

.  288.  There  are  four  conditions  which  are  to  be  regarded 
as  indispensable  in  the  construction  of  all  drains  from  all 
buildings  whatsoever.  These  conditions  are — First.  That  the 
entire  length  of  drain  is  to  be  constructed  and  maintained 
with  snffidtnt  declivity  towards  the  discharge  into  the  sewer 
to  enable  the  average  proportion  and  quantity  of  liquid  and 
solid  matters  committed  to  it  to  maintain  a  constant  and 
ufdTilerruped  Diotion^  and  that  stagnati£>n  shall  never  occur. 


162 


RUDIMENTS  OF  THE 


Second.  That  the  entire  length  of  drain  is  to  be  constructed 

and  maintained  in  a  condition  of  cmiplete-  impermeahility,  so 
that  no  portion  of  the  matters  put  into  it  should  escape  from 
it.  Third.  That  the  head  of  the  drain  shall  be  so  efficiently 
trapped  that  no  gaseous  or  volatile  properties  or  products 
can  possibly  arise  from  its  contents.  Fourth,  That  the 
lower  extremity  of  the  drain,  or  the  point  of  its  communica- 
tion With  the  sewer,  shall  be  so  properly,  completely,  and 
durably  formed,  that  no  interruption  to  the  flow  of  the 
drainage  or  escape  shall  take  place,  and  that  no  facility  shali 
be  offered  for  the  upward  progress  of  the  sewerage  in  case  the 
sewer  becomes  surcharged,  and  thus  tends  to  produce  such 
an  effect. 

289.  The  common  occuption  of  the  basement  stories  of 
houses,  as  kitchens  and  water  closets,  has  made  it  appear 
desireable  to  depress  the  drains  and  sewers,  in  order  to 
receive  the  refuse  matters  beioiv  the  level  of  these  base- 
ments ;  but  as  this  object  involves  one  or  both  of  the  evils 
we  have  pointed  out,  viz  :  deficient  declivity  and  consequent 
stagnation  in  the  drains,  and  a  general  system  of  sewers 
sunk  so  deeply  in  the  ground  that  incomparable  expense  and 
difficulty  are  created  in  construction,  access,  and  repairs,  the 
purpose  of  basement  draining  should  be  abandoned,  and 
practicable  methods  sought  of  delivering  the  entire  drainage 
at  the  level  of  the  surface  ground. 

290.  Brick- work  does  not  seem  to  be  peculiarly  fitted  for 
drains.  It  requires  smoothness  and  tightness.  Stoneware^ 
Is  more  economical  for  this  purpose  than  iron  tubing,  and  is 
entirely  free  fi^om  the  chance  of  corrosion  and  permeability. 
By  glazing  the  interior  surface,  moreover,  tubes  of  this  ware 
are  made  peculiarly  suitable  for  adoption  in  forming  drains  ; 
and  carefully  made  socket  joints  laid  in  the  direction  c^f  the 
current  are-  cheaply  executed,  if  moulded  conically  and  luted 
with  a  little  cement  of  the  best  quality.  The  size  of  the 
drain  pipes  has  to  be  graduated  accarding  to  the  quantity  to 
be  passed  through  them. 


ART  OF  BUILDING. 


153 


291.  The  trapping  of  the  head  of  the  drain,  so  as  to  pre- 
vent the  ascent  of  smell  and  impure  gas  from  the  drain  into 
the  building,  is  an  indispensable  requirement  in  draining  ap- 
paratus. Simplicity  of  construction  and  permanence  of 
action  are,  of  course,  required,  with  the  least  original  outlay 
at  which  these  qualities  can  be  obtained. 

292.  The  lower  connection  of  the  house  drain  with  the 
public  sewer  is  the  last  point  of  importance  to  which  we  al- 
lude. A  perfect  construction  of  this  portion  of  the  work 
has  always  been  recognised  as  an  essential  feature  of  good 
drainage.  The  level  of  the  bed  of  the  drain  must  be  kept 
as  high  as  possible  above  that  of  the  receiving  sewer.  If 
the  sewer  be  also  constructed  of  the  glazed  stone  ware  pip- 
ing, lengths  of  it  may  be  introduced  at  convenient  intervals, 
having  outlet  sockets  for  receiving  the  ends  of  the  house- 
drains,  and  being  slightly  tapered  or  conical  in  form  will  be 
readily  jointed  with  a  little  of  the  best  cement.  If  the  sewer 
be  constructed  of  brickwork,  a  good  joint  will  be  obtained 
by  introducing  a  separate  socket  of  stone-ware  to  receive 
the  house-drain  pipe,  and  formed  with  a  flange  at  the  other 
end  to  surround  and  cover  the  opening  in  the  sewer,  which 
can  then  be  made  good  with  a  ring  of  cement  carefullly  ap- 
plied. 

Means  of  access  to  house-drains  are  always  desirable  in 
arranging  the  details  of  the  apparatus. 

PAINTS. 

293.  Before  you  commence  to  paint  a  building,  all  holes, 
nail  heads,  and  indentations  should  be  filled  in  with  putty. 
The  priming  should  then  be  put  on.  The  color  will,  of  course, 
depend  on  the  color  of  the  paint  to  be  put  on.  After  the 
priming  is  perfectly  dry,  follow  with  another  coat  of  priming, 
or  a  coat  of  paint. 

Nut  oil  is  better  than  linseed  oil,  to  be  mixed  with  paint, 
that  requires  exposure  to  the  weather. 


154 


RUDIMENTS  OF  THE 


294.  Painters  require  a  ^aint  jpot  in  which  to  carry  their 
paint,  brushesj  with  Avhich  to  put  it  on,  ^pencils,  or  small,  soft 
brushes  for  fine  work,  a  palette,  or  small,  thin,  oval  shaped 
board  on  which  to  spread  paint  when  delicate  work  is  being 
done,  a  moll  stick ,  with  which  to  steady  the  hand. 

We  cannot  give  recipes  for  making  the  various  kinds  of 
varnish  and  paints  in  this  work. 


ABT  OF  BUILDING, 


155 


SECTION  Y. 

WOn^KmG  DRAWINGS,  SPECIFICATIONS,  ES- 
TIMATES,  AND  CONTRACTS. 

295,  The  erection  of  buildings  of  any  considerable  magni- 
tude is  usually  carried  on  under  the  superintendence  of  a 
professional  architect,  whose  duties  consist  in  the  prepara- 
tion of  the  various  working  drawings  and  specifications  that 
may  be  required  for  the  guidance  of  the  builder  ;  in  the 
strict  supervision  of  the  work  during  its  progress,  to  insure 
that  his  instructions  are  carried  out  in  a  satisfactory  manner; 
and  in  the  examination  and  revision  of  all  the  accounts  con- 
nected with  the  works. 

This  brief  enumeration  erf  the  duties  of  an  architect  will 
suffice  to  show  how  many  qualifications  are  required  in  one 
who  aims  at  being  thoroughly  competent  in  his  profession. 
He  must  unite  the  taste  of  the  artist  with  the  science  and 
practical  knowledge  of  the  builder,  and  must  be  at  the  same 
time  conversant  with  mercantile  affairs,  and  counting-house 
routine,  in  order  that  he  may  avoid  involving  his  employer 
in  the  trouble  and  expense  attendant  on  disputed  accounts, 
which  generally  are  the  result  of  the  want  of  a  clear  and 
explicit  understanding,  on  the  part  of  the  builder,  of  the 
obligations  and  responsibilities  of  engagements  based  upon 
the  incomplete  drawings,  or  vaguely  worded  specifications 
of  an  incompetent  architect. 

296.  The  profession  of  the  architect  and  the  trade  of  the 
builder  are  sometimes  carried  on  by  the  same  person  :  but 
this  union  of  the  directive  and  executive  functions  is  not  to 
be  recommended  ;  in  the  first  place,  because  the  duties  of  the 
workshop  and  the  builder^s  yard  leave  little  time  for  the 
study  of  the  higher  branches  of  architectural  knowledge  ; 


156 


RUDIMENTS  OF  THE 


and,  in  the  second  place,  because  the  absence  of  professional 
control  will  always  be  a  strong  temptation  to  a  contractor  to 
prefer  his  own  interests  to  those  of  his  employer,  however 
competent  he  may  be  to  design  the  buildings  with  the  execu- 
tion of  which  he  may  be  charged. 

During  the  present  century,  the  impulse  given  to  our  arts 
and  manufactures,  and  the  improvements  effected  in  the  in- 
ternal communications  of  the  country,  have  given  rise  to  the 
execution  of  many  extensive  works  requiring  for  their  con- 
struction a  large  amount  of  mechanical  and  scientific  know- 
*  ledge  ;  in  consequence  of  which  a  new  and  most  important 
profession  has  sprung  up  during  the  last  thirty  years,  occu- 
pying a  middle  position  between  those  of  architecture  and 
mechanical  engineering,  viz.,  that  of  the  civil  engineer.  The 
practice  of  the  architect  and  of  the  civil  engineer  so  closely 
approximate  in  many  respects,  that  it  is  difficult  strictly  to 
draw  the  line  of  demarcation  between  them  ;  but  it  may  be 
said  in  general  terms  that  whilst  the  one  is  chiefly  engaged 
in  works  of  civil  and  decorative  architecture,  such  as  the 
erection  of  churches,  public  buildings,  and  dwelHng-houses, 
the  talent  of  the  other  is  principally  called  forth  in  the  art 
of  construction  on  a  large  scale,  as  applied  to  retaining  walls, 
bridges,  tunnels,  light-houses,  &c.,  and  works  connected  with 
the  improvements  of  the  navigation  and  internal  communi- 
cations of  the  country. 

297.  The  business  of  the  surveyor  is  often  carried  on  as  a 
distinct  branch  of  architectural  practice  ;  and,  as  the  title 
of  surveyor  is  often  appropriated  to  those  who  have  no  real 
claim  to  it,  a  few  words  on  a  surveyor's  duties  may  not  be  here 
out  of -place. 

Surveyors  may  be  divided  into  three  classes  :  land  sur- 
veyors, engineerino;  surveyors,  and  building  surveyors. 

The  business  of  an  engineering  surveyor,  as  distinguished 
from  that  of  a  land  surveyor,  chiefly  consists  in  the  prepara- 
ration  of  accurate  plans,  sections,  and  other  data  relative  to 


ART  OF  BUILDING. 


157 


the  intended  sites  of  large  works,  which  may  be  required  by 
the  architect  or  engineer  preparatory  to  making  out  his 
working  drawings,  and  in  conducting  leveling  operations 
for  drainage  works,  canals,  railways,  &c. 

The  building  surveyor  prepares,  from  the  drawings  and 
specifications  of  the  architect  or  the  engineer,  bills  of  quanti- 
ties of  intended  works,  for  the  use  of  the  builder  on  which  to 
frame  his  estimates  ;  and,  in  the  case  of  contracts,  these  bills 
of  quantities  form  the  basis  of  the  engagements  entered  into 
by  the  builder  and  his  employer,  the  surveyor  being  pecuniarly 
answerable  for  any  omissions.  The  surveyor  is  also  employed 
in  the  measurement  of  works  already  executed  or  in  progress  ; 
in  the  latter  case,  for  the  purpose  of  ascertaining  the  advances 
to  be  made  at  stated  intervals,  and  is  engaged  generally  in 
all  business  connected  with  builders'  accounts. 

298.  The  following  is  the  general  routine  of  proceedings 
in  the  case  of  large  works.  It  will  readily  be  understood 
that  in  small  works  subdivision  of  labor  is  not  carried  to 
such  an  extent,  the  architect  superintending  the  works  him- 
self, without  the  aid  of  a  clerk  of  works,  and  the  builders 
taking  out  their  own  quantities. 

I.  The  general  design  having  been  approved  of,  and  the 
site  fixed  upon,  an  exact  plan  is  made  of  the  ground,  the 
nature  of  the  foundation  examined,  and  all  the  levels  taken 
that  may  be  required  for  the  preparation  of  the  working 
drawings. 

II.  The  architect  makes  out  the  working  drawings,  and 
draws  up  the  specification  of  the  work. 

III.  A  meeting  is  held  of  builders  proposing  to  tender  for 
the  execution  of  the  proposed  works,  called  either  by  public 
advertisement  or  private  invitation,  at  which  a  surveyor  is 
appointed  in  their  behalf  to  take  out  the  quantities.  Some- 
times two  surveyors  are  appointed,  one  on  the  part  of  the 
builders,  and  one  on  the  part  of  the  architect,  who  take 


158 


RUDIMENTS  OF  THE 


out  the  quantities  together,  and  check  each  other  as  they 
proceed. 

TV.  The  surveyor  having  furnished  each  party  proposing 
to  tender  with  a  copy  of  the  bills  of  quantities,  the  builders 
prepare  their  estimates,  and  meet  a  second  time  to  give  in 
their  tenders,  after  which  the  successful  competitor  and  the 
employer  sign  a  contract,  drawn  up  by  a  solicitor,  binding 
the  proper  execution  of  the  works,  and  the  other  to  the  pay- 
ment of  the  amount  of  their  cost  at  such  times  and  in  such 
sums  as  may  be  set  forth  in  the  specification. 

V.  The  work  is  then  set  out,*  and  carried  on  under  the 
constant  direction  of  a  foreman  on  the  part  of  the  builder, 
and  on  the  part  of  the  architect  under  the  superintendence 
of  an  inspector  or  clerk  of  works,  whose  duty  it  is  to  be  con- 
stantly on  the  spot  to  check  the  quality  and  quantity  of 
material  used,  to  see  to  the  proper  execution  of  the  work, 
and  to  keep  a  record  of  every  deviation  from  the  drawings 
that  may  be  rendered  necessary  by  the  wishes  of  the  employ- 
er, or  by  local  circumstances  over  which  the  architect  has 
no  control. 

The  work  is  measured  up  at  regular  intervals,  and  pay-- 
ments  made  on  account  to  the  builder,  upon  the  architect's 
certificate  of  the  amount  of  work  done. 

VI.  The  work  being  completed,  the  extras  and  omissions 
are  set  against  ea6h  other,  and  the  difference  added  to  or 
deducted  from  the  amount  of  the  contract,  and  the  whole 
business  is  concluded  by  the  architect  giving  a  final  certifi- 
cate for  the  payment  of  the  balance  due  to  the  builder. 

*  On  Setting  out  Work. — The  determinfition  of  the  exact  position  of  an  intended 
building  being  sometimes  difficult  to  accomplish,  a  few  remarks  on  the  subject 
may  be  acceptable. 

The  setting  out  of  the  leading  lines  is  simple  enough  on  level  ground,  where 
nothing  occurs  to  interrupt  the  view,  or  to  prevent  the  direct  measurement  of 
the  required  distances  ;  but  to  perform  this  operation  at  the  bottom  of  a  foun- 
dation pit,  blocked  up  with  balks  and  shores  and  ankle-de^p  in  slush,  requires  a 
degree  of  practice  and  patience  not  always  to  be  met  with.   Let  us  take  a  simple 


ART  OF  BUILDINa. 


169 


Fig.  103. 


L 


299.  Plan  of  Site. — In  preparing  the  plan  of  the  site  of 
the  proposed  works,  the  operations  of  the  surveyor  will 

case,  such  as  the  putting  in  the  abutment  of  a  bridge  or  a  viaduct,  any  error  in  the 
position  of  which  would  render  the  work  useless  (see  fig.  103)  The  leading  lines 
having  been  laid  down  on  the  drawings,  the  first  thing  to  be  done,  before  breaking 
ground,  is  to  set  out  the  centre  line  very  carefully  with  a  theodolite  and  ranging 
rods  for  a  considerable  distance  on  each  side  of  the  work,  and  to  fix  its  position  by 
erecting  poles,  planed  true  and  placed  perfectly  upright,  in  some  part  of  the  line 
where  there  is  no  chance  of  their  being  disturbed. 

Next,  the  exact  position  of  the  abutment  on  the  centre  line  would  be  decided 
upon,  and  fixed  by  setting  out  another  line  at  right  angles  to  the  first,  as  c  d.  which 
would  also  be  extended  beyond  the  works,  and  its  position  fixed  by  driving  in  stakes, 
the  exact  position  of  the  line  on  the  head  of  the  stake  being  marked  by  a  saw  cut. 

These  guiding  lines  having  now  been  permanently  secured,  the  plan  of  the  abut- 
ment may  be  set  out  on  the  ground,  the  dams  driven,  and  the  earth  got  out  to  the 
required  depth.  By  the  time  the  excavation  is  ready  for  commencing  the  work,  it 
generally  presents  a  forest  of  stays,  struts,  and  shores  that  would  defy  any  attempt 
at  setting  out  the  work  on  its  own  level  ;  it  must  therefore  be  set  out  at  the  top  of 
the  dam,  and  the  points  transferred  or  dropped,  as  follows  :  — 

First,  the  position  of  the  centre  line  is  ascertained  by  reference  to  the  poles,  and 
nails  being  driven  into  the  timbers  at  the  sides  of  the  dam,  a  fine  line  is  strained 
across  ;  the  position  of  the  line  c  d  is  found,  and  a  second  line  strained  across  in  the 
same  way.  In  a  similar  manner  other  lines  are  strained  from  side  to  side  at  the 
required  distances,  the  length  being  measured  from  the  line  c  d,  and  the  widths 
from  a  b,  until  the  outline  of  the  foundation  course  is  found  ;  the  angle  points  are 
then  transferred  to  the  bottom  of  the  excavation  by  means  of  plumb-lines,  and 
the  work  is  commenced,  its  accuracy  being  easily  tested  by  measurements  from 
the  lines  a  &  and  o  d,  until  it  is  so  far  advanced  as  to  render  this  unnecessary. 


160 


RUDIMENTS  OF  THE 


generally  have  to  be  extended  beyond  the  spot  of  ground  on 
which  the  building  is  to  stand.  The  frontages  of  the  ad- 
jacent buildings,  and  the  position  of  all  existing  or  contem- 
plated sewers,  drains  and  water-courses,  should  be  correctly 
ascertained  and  laid  down.  Sketches  drawn  to  scale  of  the 
architectural  sketches  of  the  adjacent  buildings,  if  in  town, 
and  accurate  outline  sketches  of  the  incidents  of  the  locality 
of  the  intended  operations,  if  in  the  country,  should  accom- 
pany the  plan,  that  the  architect  may  try  the  effect  of  his 
design  before  its  actual  execution  renders  it  impossible  to 
remedy  its  faults. 

By  the  careful  study  of  all  these  data  the  architect  may 
hope  to  succeed  in  making  his  works  harmonize  with  the 
objects  that  surround  them  ;  without  them,  failure  on  this 
head  is  almost  a  certainty.  ^ 

300.  Levels. — Where  the  irregularities  of  the  ground  are 
considerable,  it  is  necessary  to  ascertain  the  variations  of  the 
surface  before  the  depth  of  the  foundations  and  the  position 
of  the  floors  can  be  decided  upon. 

It  also  frequently  happens  that  the  levels  of  the  floors  and 
other  leading  lines,  in  a  new  building,  are  regulated  by  the 
capabilities  of  sewerage  or  drainage,  or  by  the  heights  of 
other  buildings  with  which  the  new  work  will  ultimately  be 
connected,  as  in  the  case  of  new  streets.  It  therefore 
becomes  of  importance  to  have  simple  and  accurate  means 
of  ascertaining  and  recording  the  relative  heights  of  differ- 
ent points.  For  this  purpose  both  the  spirit  level  and  the 
mason^s  level  are  used. 

301.  Where  the  ground  to  be  leveled  over  is  limited  in 
extent,  and  the  variations  of  level  do  not  exceed  12  feet,  the 
heights  of  any  points  may  be  found  with  the  mason's  level 
in  the  following  manner.    ( fig.  104.) 


ART  OF  BUILDING. 


161 


Fig.  104. 


In  a  convenient  place,  near  the  highest  part  of  the  ground, 
drive  three  stout  stakes  at  equal  distances  from  each  other, 
and  nail  to  them  three  pieces  of  stout  plank,  placed  as 
shown  in  the  cut,  their  upper  edges  being  adjusted  to  the 
same  horizontal  plane  by  means  of  the  mason^s  level.  The 
level  being  then  placed  on  this  frame,  an  assistant  proceeds 
to  the  first  point  of  which  the  height  is  required,  holding  up 
a  rod  with  a  sliding  vane,  which  he  raises  or  lowers  iu 
obedience  to  the  directions  of  the  surveyor,  until  it  coincides 
with  a  pair  of  sights  fixed  at  the  bottom  of  the  level  ;  the 
height  of  the  vane  will  then  be  the  difference  of  level 
between  the  top  of  the  leveling  frame,  and  the  place  where 
the  staff  was  held  up. 

302.  The  above  and  similar  methods  will  suffice  for  taking 
levels  in  a  rough  way  for  the  ordinary  purposes  of  the 
builder  ;  but  where  great  accuracy  is  requisite,  or  where  the 
levels  have  to  be  extended  over  a  considerable  distance,  as 
is  often  the  case  in  drainage  works,  the  use  of  a  more  perfect 
contrivance  is  necessary,  and  the  spirit  level  is  the  instru- 
ment principally  used  for  this  purpose. 

The  spirit  level  consists  of  a  telescope  mounted  on  a 
portable  stand,  and  furnished  with  screw  adjustments,  by 
means  of  which  it  can  be  made  to  revolve  in  a  horizontal 
plane,  any  deviation  from  which  is  indicated  by  the  motion 
of  an  air-bubble  in  a  glass  tube  fixed  parallel  to  the 
telescope. 

The  eye-piece  of  the  telescope  is  furnished  with  cross- 
wires,  as  they  are  technically  termed,  made  of  spiders' 
thread,  of  which  the  use  will  be  presently  explained. 

303.  The  leveling  staff,  now  in  common  use,  is  divided 

11 


162 


RUDIMENTS  OF  THE 


into  feet,  tenths,  and  hundredths,  in  a  conspicuous  manner, 
so  that,  with  the  help  of  the  glass,  every  division  can  be 
distinctly  seen  at  the  distance  of  one  hundred  yards  or  more. 
The  mode  of  conducting  the  operation  of  leveling  is  as 
follows  : — 

The  surveyor  having  set  up  and  adjusted  his  instrument, 
the  staff-holder  proceeds  to  the  point  at  which  the  levels  are 
to  commence,  and  holds  up  his  staff  perfectly  upright  and 
turned  towards  the  surveyor,  who  notes  the  division  of  the 
staff  which  coincides  with  the  horizontal  wire  in  the  teles- 
cope, and  enters  the  same  in  his  level-book  ;  the  staff- 
holder  then  proceeds  to  the  next  point,  and  the  reading  of 
the  staff  is  noted  as  before  ;  and  this  is  repeated  until  the 
distance  or  the  difference  of  level  makes  it  necessary  for  the 
surveyor  to  take  up  a  fresh  position.  While  this  is  being 
done,  the  staff-holder  remains  stationary,  until,  the  level 
being  adjusted  again,  he  carefully  turns  the  face  of  the  staff 
so  as  to  be  visible  from  the  instrument  in  its  new  position, 
and  a  second  reading  of  the  staff  is  noted,  after  which  he 
proceeds  forward  as  before  for  a  fresh  set  of  observations. 

304.  In  every  set  of  observations  the  first  is  called  a 
Backsight,  and  the  last  a  Foresight.  The  remaining  obser- 
vations are  called  intermediates,  and  are  entered  according- 
ly. It  will  be  seen  that  an  error  in  an  intermediate  reading 
is  confined  to  the  point  where  it  occurs  ;  but  a  mistake  in  a 
back  or  foresight  is  carried  throughout  the  whole  work,  and 
therefore  every  care  should  be  taken  to  insure  accuracy  in 
observing  these  sights. 

305.  The  surveyor  should  commence  and  close  his  work 
by  setting  the  staff  on  some  well-defined  mark,  which  can 
readily  be  referred  to  at  any  subsequent  period,  such  as  a 
door-step,  plinth  of  a  column,  &c.  These  marks  are  called 
bench  marks,  written  B  M,  and  are  essential  for  either 
checking  the  work  or  carrying  it  on  at  a  subsequent  period. 


ART  OF  BUILDING. 


163 


806.  The  reduction  of  the  levels  to  a  tabular  form  for  use 
is  a  simple  arithmetical  operation,  which  will  be  readily 
understood  by  examination  of  the  annexed  example  of  a 
level  book,  and  of  the  accompanying  section*,  fig.  105.  The 
difference  between  the  successive  readings  in  any  set  of 


Fig.  105. 


observations  is  the  difference  of  level  between  the  points 
where  the  staff  was  successively  held  up,  and  by  simple 
addition  or  subtraction,  according  as  the  ground  rises  or 
falls,  we  might  obtain  the  total  rise  or  fall  of  the  ground 
above  or  below  the  starting  point  ;  but  as  this  would  require 
two  columns,  one  for  the  total  rise,  and  one  for  the  total 
fall,  it  is  simpler  to  assume  the  starting  point  to  be  some 
given  height  above  an  imaginary  horizontal  datum  line,  drawn 
below  the  lowest  point  of  the  ground,  to  which  level  all  the 
heights  are  referred  in  the  column  headed  total  height  above 
datum  line, 

301.  The  accuracy  of  the  arithmetical  computations  is 

*In  plotting  sections  of  ground,  it  is  usual  to  make  the  vertical  scale  much 
greater  than  the  horizontal^  which  enables  small  variations  of  level  to  be  easily 
measured  on  the  drawing  without  its  being  extended  to  an  inconvenient  length. 
This  is  shown  in  the  lower  half  of  fig.  105.  The  upper  part  of  the  figure  shows  the 
section  plotted  to  the  same  horizontal  and  vertical  scale. 


164 


RUDIMENTS  OF  THE 


proved  by  adding  up  the  foresights  and  backsights,  and,  de- 
ducting the  sum  of  the  former  from  that  of  the  latter  (the 
height  of  the  first  B  M  having  been  previously  entered  at 
the  top  of  the  page  as  a  backsight),  the  remainder  will  be 
the  height  of  the  last  B  M,  and  should  agree  with  the  last 
figures  in  the  column  of  total  heights. 

308.  In  leveling  the  site  of  a  proposed  building,  if  no 
suitable  object  presents  itself  for  a  permanent  B  M  for  future 
reference,  a  large  stake,  hooped  with  iron,  should  be  driven 
into  the  ground  in  some  convenient  place  where  it  will  not 
be  disturbed.  The  height  of  this  stake  being  then  carefully 
noted  and  marked  upon  the  elevations  and  sections  of  the 
building,  it  will  serve  as  a  constant  check  on  the  depths  of 
the  excavations,  and  the  heights  of  the  different  parts  of  the 
work,  until  the  walls  reach  the  level  of  the  principal  floor,- 
w^hen  it  will  no  longer  be  required. 

309.  We  must  not  leave  the  subject  of  levels  without 
mentioning  a  very  useful  instrument,  called  the  water  level, 
which  consists  of  a  long  flexible  ]ipe,  filled  with  water,  and 
terminating  at  each  end  in  an  open  glass  tube.  When  it  is 
required  to  find  the  relative  heights  of  any  two  points,  as, 
for  instance,  the  relative  levels  of  the  floors  of  two  adjoining 
houses,  the  two  ends  of  the  tube  are  taken  to  the  respective 
points,  the  tube  being  passed  down  the  staircases,  over  the 
roofs,  or  along  any  other  accessible  route,  no  matter  how 
circuitous,  and  the  required  levels  are  found  by  measuring 
up  from  the  floors  to  the  surface  of  the  water,  which  will  of 
course  stand  at  the  same  level  at  each  end  of  the  tube. 

WORKING  DRAWINGS. 

310.  The  architect,  being  furnished  with  the  plan  and 
levels  of  the  site  of  his  operations,  and  having  caused  a  care- 
ful examination  to  be  made  of  the  probable  nature  of  the 
foundation  by  digging  pits  or  taking  borings,  proceeds  to 
make  out  his  w^orking  drawings. 


ART   OP  BUILDING. 


165 


166 


RUDIMENTS  OF  THE 


It  is  not  sufficient  for  the  execution  of  the  working  draw- 
ings that  the  draughtsman  should  be  acquainted  with  the 
ordinary  principles  of  geometric  projection.  He  must  also 
be  thoroughly  conversant  with  perspective,  and  with  the 
principles  of  chiascuro,  or  light  and  shade,  or  he  will  work 
at  random,  as  the  geometrical  projections  which  are  required 
for  the  use  of  the  workman  give  a  very  false  idea  of  the 
effect  the  work  will  have  in  execution. 

311.  Working  drawings  may  be  divided  under  three 
heads,  viz. : — Block  plans,  General  drawings,  and  Detail 
drawings  : 

I.  Block  plans. — These  show  the  outline  only  of  the  in- 
tended building,  and  its  position  with  regard  to  surrounding 
objects.  They  are  drawn  to  a  small  scale,  embracing  the 
whole  area  of  the  site,  and  on  them  are  marked  the  existing 
boundary  walls,  sewers,  gas  and  water  mains,  and  all  the 
new  walls,  drains,  and  water-pipes,  and  their  proposed  con- 
nection with  the  existing  ones,  so  that  the  builder  may  see 
at  a  glance  the  extent  of  his  operations. 

A  well-digested  block  plan,  with  its  accompanying  levels, 
showing  the  heights  of  the  principal  points,  the  fall  of  the 
drains,  &c.,  is  one  of  the  first  requisites  in  a  complete  set  of 
working  drawings. 

II.  Gemral  Drawings. — These  show  the  whole  extent  of 
the  building,  and  the  arrangement  and  connection  of  the 
different  parts  more  or  less  in  detail,  according  to  its  size 
and  extent.  These  drawings  consist  of  Flans  of  the  founda- 
tions, and  of  the  different  stories  of  the  building,  and  of  the 
roofs  ;  Elevations  of  the  different  fronts  ;  and  Sections  show- 
ing the  heights  of  the  stories,  and  such  constructive  details 
as  the  scale  will  admit  of.  These  drawings  are  carefully 
figured,  the  dimensions  of  each  part  being  calculated,  and 
its  position  fixed  by  reference  to  some  well-defined  line  in 
the  plans  or  elevations,  the  position  of  which  admits  of  easy 


ART  OF  BUILDING. 


16T 


Fig.  106 


verification  in  all  stages  of  the  work.  This  is  best  done  by 
ruling  faint  lines  on  the  drawings,  through  the  principal 
divisions  of  the  design,  as  shown  in  fig.  106,  where  the  plan 
and  elevation  are  divided  into  compartments,  by  lines  pass- 
ing through  the  centres  of  the  columns,  from  which  all  the 
dimensions  are  dated  each  way.  These  centre  lines  are,  iii 
the  execution  of  the  work,  kept  constantly  marked  on  the 
walls  as  they  are  carried  up,  so  that  they  are  at  all  times 
available  for  reference. 

By  this  means,  the  centre  lines  having  been  once  carefully 
marked  on  the  building,  any  slight  error  or  variation  from 
the  drawings  is  confined  to  the  spot  where  it  occurs,  instead 
of  being  carried  forward,  as  is  sometimes  the  case,  to  appear 
only  when  correction  is  as  desirable  as  it  is  impossible. 

The  use  of  these  centre  lines  also  saves  much  of  the  labor 
of  the  draughtsman,  as  they  form  a  skeleton,  of  which  only 
so  much  need  be  filled  up  as  may  be  required  to  show  the 
design  of  the  work. 

III.  Detailed  Draivings. — These  are  on  a  large  scale, 
showing  those  details  of  construction  which  could  not  be 


168  RUDIMENTS  OF  THE 

explained  in  the  general  drawings,  sucli  as  the  framing  of 
floors,  partitions,  and  roofs,  for  the  use  of  the  carpenter  ; 
the  patterns  of  cast-iron  girders  and  story  posts  for  the  iron- 
founder  ;  decorative  details  of  columns,  entablatures,  and 
cornices,  for  the  carver  ;  the  requisite  details  being  made 
out  separately,  as  far  as  possible,  for  each  trade  ;  which 
arrangement  saves  much  time  that  would  otherwise  be 
wasted  in  referring  from  one  drawing  to  another,  and,  which 
is  still  more  important,  insures  greater  accuracy,  from  the 
workman  understanding  better  the  nature  of  his  work. 

In  making  the  detailed  drawings  every  particular  should 
be  enumerated  that  may  be  required  for  a  perfect  under- 
standing of  the  nature  and  extent  of  the  work.  Thus,  in 
preparing  the  drawings  for  the  iron-founder,  every  separate 
pattern  should  be  drawn  out,  and  the  number  stated  that 
will  be  required  of  each. 

This  principle  should  be  attended  to  throughout  the  whole 
of  the  detailed  drawings,  as,  in  the  absence  of  such  data,  it 
is  very  difficult  to  prepare  correct  estimates  for  the  execu- 
tion of  the  work,  without  devoting  more  time  to  the  study 
of  the  drawings  than  can  generally  be  obtained  for  that 
purpose. 

SPECIFICATION". 

312.  The  drawings  being  completed,  the  architect  next 
draws  up  the  specification  of  the  intended  works.  This  is 
divided  under  two  principal  heads — 1st,  the  conditions  of 
the  contract  ;  and,  2d,  the  description  of  the  work. 

The  title  briefly  states  the  nature  and  extent  of  the  works 
to  be.  performed,  and  enumerates  the  drawings  which  are  to 
accompany  and  to  form  part  of  the  written  specification. 

313.  Conditions  of  Contract. — Besides  the  special  clauses 
and  provisions  which  are  required  by  the  particular  circum- 
stances of  each  case,  the  following  clauses  are  inserted  in  all 
specifications : 


ART  OF  BUILDING. 


169 


1.  The  works  are  to  be  executed  to  the  full  intent  and 
meaning  of  the  drawings  and  specification,  and  to  the  satis- 
faction of  the  architect. 

2.  The  contractor  to  take  the  entire  charge  of  the  works 
during  their  progress,  and  to  be  responsible  for  all  losses 
and  accidents  until  their  completion. 

3.  The  architect  is  to  have  power  to  reject  all  improper 
materials  or  defective  workmanship,  and  to  have  full  control 
over  the  execution  of  the  works,  and  free  access  at  all  times 
to  the  workshops  of  the  contractor  where  any  work  is  being 
prepared. 

4.  Alterations  in  the  design  are  not  to  vitiate  the  con- 
tract, but  all  extra  or  omitted  works  are  to  be  measured 
and  valued  according  to  a  schedule  of  prices  previously 
agreed  upon. 

5.  The  amount  of  the  contract  to  be  paid  by  instalments 
as  the  works  proceed,  at  the  rate  of  —  per  cent,  on  the 

amount  of  work  done,  and  the  balance  within  from 

the  date  of  the  architect's  final  certificate. 

Lastly.  The  works  are  to  be  completed  within  a  stated 
time,  under  penalties  which  are  enumerated. 

314.  Tht  descrijption  of  the  works  details  minutely  the 
quality  of  the  materials,  and  describes  the  manner  in  which 
every  portion  of  the  work  is  to  be  executed,  the  fulness  of 
the  description  depending  on  the  amount  of  detailed  infor- 
mation conveyed  by  the  working  drawings,  care  being  taken 
that  the  drawings  and  specification  should,  together,  contain 
every  particular  that  is  necessary  to  be  known  in  order  to 
make  a  fair  estimate  of  the  value  of  the  work. 

315.  The  chief  merit  of  a  specification  consists  in  the  use 
of  clear  and  explicit  language,  and  in  the  systematic  arrange- 
ment of  its  contents,  so  that  the  description  of  each  portion 
of  the  work  shall  be  foui^id  h\  its  proper  place  y  to  facilitate 


170 


KUDIMENTS  OF  THE 


reference,  every  clause  should  be  numbered  and  have  a  mar- 
ginal reference  attached,  and  a  copious  index  should  accom- 
pany the  whole. 

BILLS  OF  QUANTITIES. 

316.  The  surveyor,  being  furnished  by  the  architect  with 
the  drawings  and  specification,  proceeds  to  take  out  the 
quantities  for  the  use  of  the  parties  who  propose  to  tender 
for  the  execution  of  the  work.  This  is  done  in  the  same 
way  that  work  is  measured  when  executed,  except  that  the 
measurements  are  made  on  the  drawings  with  a  scale  instead 
of  on  the  real  building  with  measuring  rods. 

31 1.  In  taking  out  quantities  there  are  three  distinct 
operations  :  1st,  taking  the  dimensions  of  the  several  parts 
of  the  work,  and  entering  them  in  the  dimension  book  ;  2dly, 
working  out  the  quantities,  and  posting  them  into  the 
columns  of  the  abstracts,  which  is  called  abstracting  ;  3dly, 
casting  up  the  columns  of  the  abstracts,  and  bringing  the 
quantities  into  bill. 

318,  The  dimension  book  is  ruled,  and  the  dimensions 
entered  as  in  the  following  examples  : 


Dimension. 

Quantity. 

Description. 

16 

ft.  in. 

14  0 
0  10 
0  2K 

ft.  in. 
-      38  10 

j  Memel  fir  framed  joists  to 
(     front  room  ground  floor. 

In  this  example  the  work  measured  consists  of  sixteen 
joists  ;  each  14  ft.  long  and  10  in.  deep  and  2|  in.  thick  ; 
and  the  total  quantity  of  timber  they  contain  amounts  to  38 
ft.  10  in.  cube. 


ART  OF  BtriLDING. 


Dimension. 

No.  of  bricks 
in  thickness. 

Quantity. 

Description. 

ft.  in. 

20  6 
11  6 

j- 

ft.  in. 

235  9 

)  Stock  brickwork  in  mor- 
V  tar  to  front  wall,  from 
)     footings  to  1st  set-off. 

319.  In  preparing  the  abstract  for  each  trade,  the  sur- 
veyor looks  over  his  dimensions  to  see  what  articles  he  will 
have,  and  rules  his  paper  into  columns  accordingly,  writing 
the  proper  heads  over  each. 

The  principal  point  to  be  attended  to  in  abstracting  quan- 
tities is  to  preserve  a  regular  rotation  in  arranging  the  dif- 
ferent descriptions  of  work,  so  that  every  article  may  at 
once  be  found  on  referring  to  its  proper  place  in  the  abstract. 

"No  fixed  rules  can  be  given  on  this  head,  as  the  form  of 
abstract  is  different  for  every  trade,  and  must  be  varied  ac- 
cording to  circumstances  ;  but,  as  a  general  principle,  arti- 
cles of  least  value  should  be  placed  first.  Solid  measure 
should  take  precedence  of  superficial,  and  .superficial  of  lin- 
eal, and  miscellaneous  articles  should  come  last  of  all  ;  or, 
in  technical  terms,  the  rotation  should  be,  1st,  cubes  ;  2nd, 
supers. ;  3rd,  runs  ;  and,  lastly,  miscellaneous. 

320.  In  bringing  the  quantities  into  bill,  the  same  rota- 
tion is  to  be  observed  as  in  abstracting  them,  care  being  ta- 
ken that  every  article  is  inserted  in  its  proper  place,  so  that 
it  may  readily  be  found  in  the  bill. 

The  limits  of  this  volume  prevent  our  going  into  much  de- 
tail on  the  subject  of  builders^  accounts,  and  we  must  there- 
fore confine  ourselves  to  laying  before  the  reader  a  skeleton 
estimate,  which  will  give  him  a  tolerable  idea  of  the  manner 
in  which  the  several  kinds  of  artificers^  work  are  abstracted 
and  brought  into  bill. 

321.  Estimate  for  the  Erection  of  at  ,  for 

.  ,  according  to  Specification  and  Drawings  numbered 

1  to  — ,  prepared  by  ,  Architect.  (Date.) 


RUDIMENTS  OF  THE 


yds.  ft. 

—    —  cube 


ft.  in. 


cwt.  qrs.  lbs. 


rods.  ft. 
—    —  supl 


sqrs.  ft. 


yds.  ft. 


ft.  in. 


—    —  run 


Foundations. 

Excavation  to  foundations, 
(including  cofferdams, 
pumping,  &c.)  .       .  .at 
Concrete  .... 

Timber  in  piles  driven  —  ft. 
through,  (describe  the  ma- 
terial,) including  ringing, 
shoeing  and  driving,  but 
not  ironwork  . 

Do.  in  6-in.  planking,  spiked 
to  pile-heads 

Wrought  iron  in  shoes  to 
piles 

Total  of  foundations  to  be 
carried  to  summary 

Bricklayer. 

Reduced  brickwork  in  mor- 
tar  at 

Reduced  brickwork  in  ce- 
ment 

Tiling  (describing  the  kind, 
whether  plain  or  pantiling 
if  single  or  double  latlis, 
&c.,  &c.)  . 

Brick nogging  to  partitions 
Paving,  (of  various  descrip- 
tions) 

And  all  other  articles  val- 
ued per  yard  superficial. 

Gauge  arches 

Facings  (with  superior  des- 
criptioij  of  bricks,  specify- 
ing the  quality) 

Cutting  to  arches  or  splays 
And  all  other  work  valued 
by  the  foot  superficial. 

Barrel  or  other  drains  (speci- 
fying size,  &c.)  . 


Carried  forward 


ART  OP  BUILDING. 


113 


Nos. 


yds.  ft. 
—     —  cube 


ft.  in. 

—    —  supl, 


Nos, 


sqrs.  ft. 
—    —  supl. 


Bricklayer,  continued. 

Brought  forward  . 
Tile  creasing       .       .       .at  — 
And  all  other  articles  val- 
ued by  running  measure. 
Chimney  pots,  each  ;  bedding 
and  pointing  sash  and  door 
frames,  each  ;  and  all  mis- 
c-ellaneous  articles 

Total  of  bricklayers'  work 
to  be  carried  to  summa- 
ry   ...  . 

Mason. 

Rubble  walling    .       .       .  at  - 
Hammer-dressed  walling  in 
random  courses 

Stone  (describing  the  kinds). 
Labor  on  above  (as  plain 
work,  sunk,  moulded  or 
circular  work)  . 
Hearths,  pavings,  landings, 
&c.,  beginning  with  the 
thinnest  .... 
Marble  slabs,  beginning  with 
the  thinnest  and  inferior 
qualities  .... 
Window  sills,  curbs,  steps, 

copings,  &c. 
Joggle  joints,  chases,  &c. 
Mortices  and  rail  holes,  &c. — 
dowels,  cramps,  and  other 
articles  numbered 

Total  of  masons'  work  to  be 
carried  to  summary 

Carpenter  and  Joiner. 

Labor  and   nails  to  roofs, 

floors,  or  quarter  partitions  at  ■ 
Battenings  and  boardings  ac- 
cording to  description 

Carried  forward . 


Dolls. 


CIS. 


174  RUDIMENTS  OF  THB 

Carpenter  &  Joiner,  continued. 


—  —  aupi. 


cube 


— •    —  supl. 


Nos. 


Floors,  according  to  descrip- 
tioii,  beginning  with  tlie 
interior  and  ending  witliafc 
the  best  descriptions 
And  so  on  for  all  work 
valued  by  the  square, 
Memel  fir,  according  to  des- 
cription, as  fir  bond,  fir 
framed,  wrought  and  fram- 
ed, wrought,  framed,  and 
rebated,  <fec. 
Do.  proper  door  and  window 
'    cjtses-  .... 
Then  oak,  and  superior  de- 
scriptions of  timber,  in 
the  same  way. 
Then  the  superficial  work, 
as — 

j^-in.  deal  rough  linings,  and 
so  on  with  the  different 
thicknesses  of  deals  accord- 
ing to  the  labor  on  them  ; 
arranging  them  according 
to  their  thickness,  and  the 
amount  of  labor  on  them, 
beginning  with  the  thin- 
ne&t  .  .  .  ,  . 
Then  oak  plank  or  mahog- 
any in  the  same  way. 
Then  take  the  framed  work, 
as — 

1^-in.  deal  square-framed  in- 
closure  to  closets,  and  so  on 
with  the  rest  of  the  framed 
work,  as  doors,  shutters, 
sashes,  frames,  &c.,  accord- 
ing to  description 
Then  the  work  valued  by 
running  measure,  as — 

21^-in.    Spanish  mahogany 
moulded,  grooved,  and  bea- 
ded handrail 
Then  the  numbers,  as — 

Mitred  and  turned  caps,  fix- 
ing iron  balusters,  &c. 


Carried  forward  . 


ART  OF  BUILDING. 


Carpenter  &  Joiner,  continued. 


Brought  forward  . 
Lastly  —  The  Ironmongery, 
every    article    of  which 
should  be  carefully  describ- 
ed. 

Total  of  carpenter  and 
joiners'  work  to  be  car- 
ried to  summary  . 


eqrs.  ft. 
—     —  supl, 


ft.  in. 


Nos, 


yds.  ft. 

—    —  supl, 


Slater. 

Countess,  or  any  other  kind 
of  slating,  according  to  de- 
scription .  . 
Then  slate  slab,  as — 

Inch  shelves,  rubbed  one  side, 
beginning  with  the  slabs  of 
least  thickness,  and  arrang- 
ing them  according  to  the 
labor  bestowed  on  them  . 
Then  the  work  valued  by 
running  measure,  as — 

Patent  saddle-cut  slate  ridge 
Lastly — the  numbers,  as — 

Holes,  cut,  &c. 

Total  of  slaters'  work  to  be 
carried  to  summary 

Plasterer. 

First  the  superficial  quan- 
tity of  plastering,  as  — 
Render  float  and  set  to  walls, 
beginning  with  the  com- 
monest,   and  proceeding 
through  the  different  de- 
scriptions of  two  and  three 
coat  work,  up  to  the  stuc- 
coes and  superior  work 
Then  the  whitewashing,  dis- 
tempering, &c.  . 
Next  the  run  of  corniceS; 
architraves,  reveals,  &c., 
as-— 


at 


at 


Carried  forward  . 


116 


KUDIMENTS  OF  THE 


ft.  in. 

—  run. 


N08 


tns.  ct.  qrs.  lb. 


yds.  ft. 


Plasterer,  continued. 

Brought  forward  . 
Plaiu  cornice  to  drawing- 
room,  14  in.  girt 
And  lastly  the  numbers ; 
as — 

4  mitres,  1  centre  flower,  30 
in.  diameter,  &c..  &c. 
Total  of  plasterers'  work  to 
be  carried  to  summary  . 

Smith  and  Iron-Founder. 

Begin  with  the  cast-iron 

as — 

Cast-iron  in  No.  4  girders 
including  patterns,  paint- 
ing, and  fixing  .       .  .at 
N.  B.— State  the  No.  of 

patterns. 
Then  the  smaller  castings, 

as — 

Bailings,  balconies,  columns, 

&c  

Then  the  wrought  iron, 
as — 

Wrought  iron  in  chimney 
bars,  straps,  screw  bolts 
railings,  &c. 

Then  the  articles  sold  by 
running  measure,  as — 
Cast-iron     gutters,  water- 
pipes,  &c. 

Lastly,  the  numbers,  as — 
Stoves,  coal-plates,  stable-fit- 
tings, &c.  . 

Total  smith  and  iron-foun- 
ders' work  to  be  carried 
to  summary  . 

Bell-hanger. 

Number  the  bells,  and  de- 
scribe the  mode  of  hang- 
ing, as — 


Carried  forward  . 


ART  OF  BTJIIDnTG. 


ITT 


Nos 


cwt.  qrs.  lbs, 


ft.  in. 
—    —  run. 


Nos. 


yds.  ft. 

—    —  supl, 


Bell-hanger,  continued. 

Brought  forward  . 

—  bells  hung  with  copper 
wires  in  concealed  tin 
tubes,  with  bells,  cranks, 
and  wires  complete  . 

And  then  enumerate  the  or 
namental  furniture  to  the 
different  pulls  . 

Total  of  bell-hangers'  work 
to  be  carried  to  summa- 


ry 


Plumber. 


Cast  lead  laid  in  gutters, 
hips,  ridges,  flats,  cisternS; 
&c. ;  including  all  solder, 
wall  hooks,  nails,  &c.       .  — 
Milled     do.       do.  . 
Then    socket,  rain-water, 
funnel  pipes,  and  other 
work  valued  by  the  line- 
al foot,  as — 
Inch  drawn  pipes 

Lastly  the  numbers,  as — • 
Joints,  plugs,  and  washers 
air  traps,  brass  grates, 
cocks,  copper  balls,  pumps 
water  closets,  apparatus, 
&c  

Total  of  plumbers'  work  to 
be  carried  to  summary 


Painter. 

Of  painting,  according  to  de 
scription,  specifying  the 
number  of  oils,  and  wheth- 
er common  or  extra  colors, 
beginning  with  the  work 
in  fewest  coats,  and  finish- 
ing with  the  most  expen- 
sive descriptions 


D0LL8. 


Cis. 


Carried  forward  . 


12 


178 


ft-  in. 

—    —  run 


Nos, 


ft.  in. 

  —  BUpl. 


RUDIMENTS  OF  THE 

Painter,  continued. 


Brought  forward  . 
Then  the  running  work, 
as — 

Skirtings,   plinths,  window 
sills,  &c.  . 

Lastly  the  numbers,  as— 
Frames,    squares,  chimney 
pieces,  &c. 

Total  of  painters'  work  to 
be  carried  to  summary 

Glazier. 

Glazing,  according  to  de- 
scription, specifying  size  of 
squares,  and  quality  of 
glass  .  .  .  . 
Then,  the  stained  and  other 
ornamental  glass  ;  and, 
lastly,  the  plate  glass. 

Total  of  glazier's  work  to 
be  carried  to  summary 

Paper-hanger  &  Decorator. 


yds.  ft. 

ft.  in. 
yds.  ft. 


BUpl 


run 
Nos. 


at  ■ 


Distempering, 
description 


accordino^  to 


Scagliola  slabs      do.  . 

Gold  mouldings  . 

Pieces  of  paper  hung,  ac- 
cording to  description,  in- 
cluding preparing  walls — 
Hanging,  lining,  paper 
and  punucing  do. 

Dozen  of  borders  . 

Total  of  paper-hanger  and 
decorator's  works  to  be 
carried  to  summary 


Dolls. 


Cis. 


at  — 


ART  OF  BUILDING. 


119 


Dolls, 


Ora 


Sundries. 

Temporary  fencings — watching  and  light- 
ing works 
Office  for  clerk  of  works  . 
District  surveyor's  fee 
Fire  insurance 
Surveyor's  charge  for  bills  of  quantities 

Total  sundries  to  be  carried  to  summary 

Summary  of  Bills. 


Foundations  . 
Bricklayer 
Mason  . 

Carpenter  and  joiner 
Slater 
Plasterer 

Smith  and  iron-founder 
Bell-hanger 
Plumber,  painter,  and  glazier 
Paper-hanger  and  decorator 
Sundries 

Total  amount  of  estimate 


322.  The  surveyor  furnishes  the  builder,  whose  tender  is 
accepted,  with  copies  of  the  drawings  from  which  the  quan- 
tities have  been  taken  off. 

By  reference  to  these,  the  builder  can  at  all  times  satisfy 
himself  that  the  detailed  drawins-s,  furnished  for  the  exe- 
cution  of  the  work,  contain  nothing  beyond  what  he  has  con- 
tracted for. 

Copies  of  the  drawings  and  specification  are  attached  to 
the  contract  deed,  and  are  signed  by  the  builder  and  other 
parties  respectively  concerned. 

323.  It  scarcely  ever  happens  that  a  large  undertaking 
can  be  carried  into  execution  without  considerable  departure 
from  the  contract  designs,  especially  in  the  matter  of  found- 
ations and  underground  work  ;  the  exact  nature  and  extent 
of  which  must  often  be  uncertain  until  the  works  are  com-, 
menced. 


180 


EUDIMENTS  OF  THE 


To  provide  for  these  contingencies  without  setting  aside 
the  contract,  the  builder's  estimate  is  accompanied  by  a 
schedule  of  prices  at  which  he  undertakes  to  execute  any 
additional  work  that  may  be  required,  or  to  value  any  work 
that  may  be  omitted.  This  schedule  should  be  carefully 
drawn  out,  so  that  there  shall  be  no  dispute  as  to  its  mean- 
ing ;  thus,  under  the  head  of  brickwork,  it  should  be  clearly 
understood  whether  centering  is  included  in  the  price  named, 
or  whether  it  is  to  form  an  additional  charge  ;  with  iron- 
founders'  work,  whether  the  price  includes  patterns  ;  and  so 
on  with  every  description  of  work. 

324.  Architects  are  remunerated  by  a  commission  of  5 
per  cent,  on  the  amount  expended  under  their  direction,  be- 
sides traveling  expenses,  salary  of  the  clerk  of  the  works,  and 
occasionally  other  charges,  according  to  circumstances. 


THE  END. 


II 


r 


GETTY  RESEARCH  INSTITUTE 


3  3125  01023  1427 


